Datediff mysql hours

Datediff mysql hours DEFAULT

Summary: in this tutorial, you will learn how to use the MySQL DATEDIFF function to calculate the number of days between two date values.

Introduction to MySQL function

The MySQL function calculates the number of days between two  ,  , or   values.

The syntax of the MySQL function is as follows:

Code language:SQL (Structured Query Language)(sql)

The function accepts two arguments that can be any valid date or date-time values. If you pass or values, the function only takes the date parts for calculation and ignores the time parts.

The function is useful in many cases e.g., you can calculate an interval in days that the products need to ship to a customer.

MySQL examples

Let’s take a look at some examples of using the function.

Code language:SQL (Structured Query Language)(sql)

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Code language:SQL (Structured Query Language)(sql)

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Code language:SQL (Structured Query Language)(sql)

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See the following table in the sample database.

orders table

To calculate the number of days between the required date and shipped date of the orders, you use the function as follows:

Code language:SQL (Structured Query Language)(sql)

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MySQL DATEDIFF function example

The following statement gets all orders whose statuses are in-process and calculates the number of days between ordered date and required date:

Code language:SQL (Structured Query Language)(sql)

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MySQL DATEDIFF function example remaining days

For calculating an interval in week or month, you can divide the returned value of the function by 7 or 30 as the following query:

Code language:SQL (Structured Query Language)(sql)

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MySQL DATEDIFF example

Note that the function is used to round the results.

In this tutorial, you have learned how to use MySQL function to calculate the number of days between two date values.

Sours: https://www.mysqltutorial.org/mysql-datediff.aspx

DATEDIFF function

DATEDIFF returns the difference between the date parts of two date or time expressions.

Syntax

Arguments

datepart

The specific part of the date or time value (year, month, or day, hour, minute, second, millisecond, or microsecond) that the function operates on. For more information, see Date parts for date or timestamp functions.

Specifically, DATEDIFF determines the number of date part boundaries that are crossed between two expressions. For example, suppose that you're calculating the difference in years between two dates, and . In this case, the function returns 1 year despite the fact that these dates are only one day apart. If you are finding the difference in hours between two timestamps, and , the result is 2 hours. If you are finding the difference in hours between two timestamps, and , the result is 2 hours.

date|time|timetz|timestamp

A DATE, TIME, TIMETZ, or TIMESTAMP column or expressions that implicitly convert to a DATE, TIME, TIMETZ, or TIMESTAMP. The expressions must both contain the specified date or time part. If the second date or time is later than the first date or time, the result is positive. If the second date or time is earlier than the first date or time, the result is negative.

Return type

BIGINT

Examples with a DATE column

The following example finds the difference, in number of weeks, between two literal date values.

The following example finds the difference, in number of quarters, between a literal value in the past and today's date. This example assumes that the current date is June 5, 2008. You can name date parts in full or abbreviate them. The default column name for the DATEDIFF function is DATE_DIFF.

The following example joins the SALES and LISTING tables to calculate how many days after they were listed any tickets were sold for listings 1000 through 1005. The longest wait for sales of these listings was 15 days, and the shortest was less than one day (0 days).

This example calculates the average number of hours sellers waited for all ticket sales.

Examples with a TIME column

The following example table TIME_TEST has a column TIME_VAL (type TIME) with three values inserted.

The following example finds the difference in number of hours between the TIME_VAL column and a time literal.

The following example finds the difference in number of minutes between two literal time values.

Examples with a TIMETZ column

The following example table TIMETZ_TEST has a column TIMETZ_VAL (type TIMETZ) with three values inserted.

The following example finds the differences in number of hours, between a TIMETZ literal and timetz_val.

The following example finds the difference in number of hours, between two literal TIMETZ values.

Sours: https://docs.aws.amazon.com/redshift/latest/dg/r_DATEDIFF_function.html
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MySQL DateDiff – Quick Guide Seconds, Minutes, Hours, Months, Years

So working with dates is something every MySQL database developer must do once in a while. And most of the time, this will require calculating the number of days between date values. Fortunately, MySQL provides a handy date function to make such calculations easy-breezy – say hello to the MySQL datediff function.

Therefore, in this article, we’re going to provide you with information on how to use the datediff() function. In addition, we will show you practical situations where you’ll find this function most helpful in your MySQL development journey.

Let’s go!

ALSO READ: MySQL_Connect Function: The Complete Guide to MySQL_Connect()

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What Is MySQL DateDiff Function

In the first place, let’s put things into perspective – what is MySQL datediff() function? This function allows you to determine the difference between two dates quickly. Therefore, all you have to do is to pass required input parameters to the function; and it will return a value indicating the difference between the two inputs.

Syntax

The MySQL datediff function’s syntax is pretty simple:

datediff(expression1,expression2);

Note:expression1is the first date, and expression2 is the second date.

How To Find DateDiff In MySQL

When working with MySQL database and trying to figure out how to find datediff in MySQL, all you have to do is use the MySQL datediff function.

For example, let’s you have two dates: September 1, 2023, and September 20, 2023. And you want to programmatically find the difference between the two (without using your calculator or fingers to count), you’ll use the datediff() function as follows:

Select datediff('2023-09-20','2023-09-01') as Difference;

Once you run the above query against the database, you’ll get the following result:

Notably, bear in mind that the MySQL datediff() function works with the following MySQL versions: 5.7, 5.6, 5.5, 5.1, 5.0 and 4.1.1.

What Does DateDiff Return MySQL

Equally important, you may be wondering what does the MySQL datediff function return. As you can see from the above example, the function will return the number of days between the two dates you provided.

Also, if you provided datetimes instead of date days, then the function will equally return the difference between the two provided date times in days.

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How To Use DateDiff In MySQL

Now, let’s take a look at how to use datediff() in MySQL with some practical examples so you can fully understand the concept.

MySQL DateDiff Seconds

First, how do you get the difference between two times in seconds? The datediff() function is probably not the best function to use in such a situation.

So if you’re trying to do MySQL datediff seconds, you’ll come to realize that the datediff() function only returns day values. Therefore, if you supply the seconds in the date, only the date portion is used in the calculation to return the number of days.

Now, there’s the timestampdiff() function which will provide you with the needed capability to calculate the differences between two datetime expressions. And the two expressions must be of the same type.

The syntax is as follows:

timestampdiff(unit,expression1,expression2);

And for the arguments:

1. unit: The unit can be one of the following options: FRAC_SECOND (microseconds), SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.
2. expression1: This is a datetime expression you’ll substract expression2 from.
3. expression2: This is a datetime expression you’ll substract from expression1.

Therefore, if you’re looking for MySQL DateDiff seconds, you can use the TimeStampDiff function to accomplish your objective. For example:

Select timestampdiff(SECONDS, '2023-09-20 12:30:15', '2023-09-01 10:15:00') as Difference;

The above query statement will return the different between the two datetime values provided in seconds2023-09-20 12:30:15 and 2023-09-01 10:15:00 as shown below:

MySQL DateDiff Minutes

Likewise, there will be times you need to get the difference in two datetime expression in minutes. Consequently, your natural inclination might be to there’s a MySQL DateDiff Minutes as a solution.

However, as stated above, you’ll come to realize that this won’t work out very well. Instead, use the TimeStampDiff() function to accomplish this task.

Select timestampdiff(MINUTES, '2023-09-20 12:30:15', '2023-09-01 10:15:00') as Difference;

The above query statement will return the difference between the two datetime values provided in minutes2023-09-20 12:30:15 and 2023-09-01 10:15:00 as shown below:

MySQL DateDiff Hours

Furthermore, as you can see from the above two examples when looking for the difference in two datetime expressions, the MySQL DateDiff hours is not a reliable solution.

Once again, you can use the TimeStampDiff() function to get the job done. Let’s take look:

Select timestampdiff(HOURS, '2023-09-20 12:30:15', '2023-09-01 10:15:00') as Difference;

The above query statement will return the difference between the two datetime values provided in hours2023-09-20 12:30:15 and 2023-09-01 10:15:00 as shown below:

MySQL DateDiff Days

The MySQL DateDiff() function’s default return value is the number of days between two date or datetime expressions.

And as we’ve also indicated earlier, if you run a query statement like this:

Select datediff('2023-09-20','2023-09-15') as Difference;

You’ll get the following result:

The result tells you that there’s a difference of 5 days between the two expressions. So this is how the function works.

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MySQL DateDiff Months

Of course, there will be occasions where you need to know the difference between two periods. Particularly, let’say you want to know the difference between the periods in months.

Certainly, trying to use the MySQL DateDiff Months in such a situation won’t cut. Luckily, MySQL provides another handy function called the PERIOD_DIFF() which can do the trick.

Syntax:

The PERIOD_DIFF() syntax is as follows:

period_diff(expression1,expression2);

where “expression1” indicates the first period and “expression2” means the second period to subtract from “expression1”.

So here’s an example:

Select period_diff(202310,202302) As Difference;

The above query statement will output

The result shows that there is eight months difference between the two periods.

MySQL DateDiff Years

Moreover, if you’re looking for MySQL DateDiff Years, you can accomplish the same using the PERIOD_DIFF() function above as well as the TIMESTAMPDIFF() described above as well.

For PERIOD_DIFF() example:

Select period_diff(2025,2023) As Difference;

The above query statement will return:

For TIMESTAMPDIFF() example:

Select timestampdiff(YEAR, '2025-09-20 12:30:15', '2023-09-01 10:15:00') as Difference;

The above query statement will also return:

MySQL DateDiff Current Date

Besides, you can use the function together with the Current Date function. The CURDATE() function returns the value of the current date on the system.

So here’s a practical example:

Select datediff(curdate(),'2023-09-01') as Difference;

Once you run the above query against the database, If the current date is ‘2023-09-30’, you’ll get the following result (in days):

Final Thought

We hope that this article has given you more insight into this function, it’s applications as well as limitations. As with anything, feel free to solidify your understanding of the fundamental concepts by reading other available resources as well as MySQL documentation. Good luck!

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DatePart, DateAdd and DateDiff functions in SQL Server Part 27

MySQL DATEDIFF() Function

❮ MySQL Functions

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-06-25", "2017-06-15");

Try it Yourself »

Definition and Usage

The DATEDIFF() function returns the number of days between two date values.

Syntax

DATEDIFF(date1, date2)

Parameter Values

ParameterDescription
date1, date2Required. Two dates to calculate the number of days between. (date1 - date2)

Technical Details


More Examples

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-06-25 09:34:21", "2017-06-15 15:25:35");

Try it Yourself »

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-01-01", "2016-12-24");

Try it Yourself »

❮ MySQL Functions


Sours: https://www.w3schools.com/mysql/func_mysql_datediff.asp

Mysql hours datediff

  • ,

    When invoked with the form of the second argument, is a synonym for . The related function is a synonym for . For information on the argument, see Temporal Intervals.

    When invoked with the form of the second argument, MySQL treats it as an integer number of days to be added to .

  • adds to and returns the result. is a time or datetime expression, and is a time expression.

  • converts a datetime value from the time zone given by to the time zone given by and returns the resulting value. Time zones are specified as described in Section 5.1.15, “MySQL Server Time Zone Support”. This function returns if the arguments are invalid.

    If the value falls out of the supported range of the type when converted from to UTC, no conversion occurs. The range is described in Section 11.2.1, “Date and Time Data Type Syntax”.

  • Returns the current date as a value in or format, depending on whether the function is used in string or numeric context.

  • ,

    and are synonyms for .

  • ,

    and are synonyms for .

  • ,

    and are synonyms for .

  • Returns the current time as a value in or format, depending on whether the function is used in string or numeric context. The value is expressed in the session time zone.

    If the argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

  • Extracts the date part of the date or datetime expression .

  • returns − expressed as a value in days from one date to the other. and are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

  • ,

    These functions perform date arithmetic. The argument specifies the starting date or datetime value. is an expression specifying the interval value to be added or subtracted from the starting date. is evaluated as a string; it may start with a for negative intervals. is a keyword indicating the units in which the expression should be interpreted.

    For more information about temporal interval syntax, including a full list of specifiers, the expected form of the argument for each value, and rules for operand interpretation in temporal arithmetic, see Temporal Intervals.

    The return value depends on the arguments:

    • if the argument is a value and your calculations involve only , , and parts (that is, no time parts).

    • if the first argument is a (or ) value, or if the first argument is a and the value uses , , or .

    • String otherwise.

    To ensure that the result is , you can use to convert the first argument to .

  • Formats the value according to the string.

    The specifiers shown in the following table may be used in the string. The character is required before format specifier characters. The specifiers apply to other functions as well: , , .

    SpecifierDescription
    Abbreviated weekday name (..)
    Abbreviated month name (..)
    Month, numeric (..)
    Day of the month with English suffix (, , , , …)
    Day of the month, numeric (..)
    Day of the month, numeric (..)
    Microseconds (..)
    Hour (..)
    Hour (..)
    Hour (..)
    Minutes, numeric (..)
    Day of year (..)
    Hour (..)
    Hour (..)
    Month name (..)
    Month, numeric (..)
    or
    Time, 12-hour ( followed by or )
    Seconds (..)
    Seconds (..)
    Time, 24-hour ()
    Week (..), where Sunday is the first day of the week; mode 0
    Week (..), where Monday is the first day of the week; mode 1
    Week (..), where Sunday is the first day of the week; mode 2; used with
    Week (..), where Monday is the first day of the week; mode 3; used with
    Weekday name (..)
    Day of the week (=Sunday..=Saturday)
    Year for the week where Sunday is the first day of the week, numeric, four digits; used with
    Year for the week, where Monday is the first day of the week, numeric, four digits; used with
    Year, numeric, four digits
    Year, numeric (two digits)
    A literal character
    , for any “” not listed above

    Ranges for the month and day specifiers begin with zero due to the fact that MySQL permits the storing of incomplete dates such as .

    The language used for day and month names and abbreviations is controlled by the value of the system variable (Section 10.16, “MySQL Server Locale Support”).

    For the , , , and specifiers, see the description of the function for information about the mode values. The mode affects how week numbering occurs.

    returns a string with a character set and collation given by and so that it can return month and weekday names containing non-ASCII characters.

  • See the description for .

  • is a synonym for .

  • Returns the name of the weekday for . The language used for the name is controlled by the value of the system variable (Section 10.16, “MySQL Server Locale Support”).

  • Returns the day of the month for , in the range to , or for dates such as or that have a zero day part.

  • Returns the weekday index for ( = Sunday, = Monday, …, = Saturday). These index values correspond to the ODBC standard.

  • Returns the day of the year for , in the range to .

  • The function uses the same kinds of specifiers as or , but extracts parts from the date rather than performing date arithmetic. For information on the argument, see Temporal Intervals.

  • Given a day number , returns a value.

    Use with caution on old dates. It is not intended for use with values that precede the advent of the Gregorian calendar (1582). See Section 12.9, “What Calendar Is Used By MySQL?”.

  • Returns a representation of as a datetime or character string value. The value returned is expressed using the session time zone. (Clients can set the session time zone as described in Section 5.1.15, “MySQL Server Time Zone Support”.) is an internal timestamp value representing seconds since UTC, such as produced by the function.

    If is omitted, this function returns a value.

    If is an integer, the fractional seconds precision of the is zero. When is a decimal value, the fractional seconds precision of the is the same as the precision of the decimal value, up to a maximum of 6. When is a floating point number, the fractional seconds precision of the datetime is 6.

    is used to format the result in the same way as the format string used for the function. If is supplied, the value returned is a .

    Note

    If you use and to convert between values in a non-UTC time zone and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For details, see the description of the function.

  • Returns a format string. This function is useful in combination with the and the functions.

    The possible values for the first and second arguments result in several possible format strings (for the specifiers used, see the table in the function description). ISO format refers to ISO 9075, not ISO 8601.

    Function CallResult

    can also be used as the first argument to , in which case the function returns the same values as for .

  • Returns the hour for . The range of the return value is to for time-of-day values. However, the range of values actually is much larger, so can return values greater than .

  • Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns if the argument is invalid.

  • ,

    and are synonyms for .

  • ,

    and are synonyms for .

  • Returns a date, given year and day-of-year values. must be greater than 0 or the result is .

  • Returns a time value calculated from the , , and arguments.

    The argument can have a fractional part.

  • Returns the microseconds from the time or datetime expression as a number in the range from to .

  • Returns the minute for , in the range to .

  • Returns the month for , in the range to for January to December, or for dates such as or that have a zero month part.

  • Returns the full name of the month for . The language used for the name is controlled by the value of the system variable (Section 10.16, “MySQL Server Locale Support”).

  • Returns the current date and time as a value in or format, depending on whether the function is used in string or numeric context. The value is expressed in the session time zone.

    If the argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

    returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, returns the time at which the function or triggering statement began to execute.) This differs from the behavior for , which returns the exact time at which it executes.

    In addition, the statement affects the value returned by but not by . This means that timestamp settings in the binary log have no effect on invocations of . Setting the timestamp to a nonzero value causes each subsequent invocation of to return that value. Setting the timestamp to zero cancels this effect so that once again returns the current date and time.

    See the description for for additional information about the differences between the two functions.

  • Adds months to period (in the format or ). Returns a value in the format .

    Note

    The period argument is not a date value.

  • Returns the number of months between periods and . and should be in the format or . Note that the period arguments and are not date values.

  • Returns the quarter of the year for , in the range to .

  • Returns the second for , in the range to .

  • Returns the argument, converted to hours, minutes, and seconds, as a value. The range of the result is constrained to that of the data type. A warning occurs if the argument corresponds to a value outside that range.

  • This is the inverse of the function. It takes a string and a format string . returns a value if the format string contains both date and time parts, or a or value if the string contains only date or time parts. If the date, time, or datetime value extracted from is illegal, returns and produces a warning.

    The server scans attempting to match to it. The format string can contain literal characters and format specifiers beginning with . Literal characters in must match literally in . Format specifiers in must match a date or time part in . For the specifiers that can be used in , see the function description.

    Scanning starts at the beginning of and fails if is found not to match. Extra characters at the end of are ignored.

    Unspecified date or time parts have a value of 0, so incompletely specified values in produce a result with some or all parts set to 0:

    Range checking on the parts of date values is as described in Section 11.2.2, “The DATE, DATETIME, and TIMESTAMP Types”. This means, for example, that “zero” dates or dates with part values of 0 are permitted unless the SQL mode is set to disallow such values.

    If the SQL mode is enabled, zero dates are disallowed. In that case, returns and generates a warning:

    Note

    You cannot use format to convert a year-week string to a date because the combination of a year and week does not uniquely identify a year and month if the week crosses a month boundary. To convert a year-week to a date, you should also specify the weekday:

  • ,

    When invoked with the form of the second argument, is a synonym for . For information on the argument, see the discussion for .

    The second form enables the use of an integer value for . In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression .

  • returns − expressed as a value in the same format as . is a time or datetime expression, and is a time expression.

  • Returns the current date and time as a value in or format, depending on whether the function is used in string or numeric context.

    If the argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

    returns the time at which it executes. This differs from the behavior for , which returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, returns the time at which the function or triggering statement began to execute.)

    In addition, the statement affects the value returned by but not by . This means that timestamp settings in the binary log have no effect on invocations of .

    Because can return different values even within the same statement, and is not affected by , it is nondeterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging.

    Alternatively, you can use the option to cause to be an alias for . This works if the option is used on both the replication source server and the replica.

    The nondeterministic nature of also means that indexes cannot be used for evaluating expressions that refer to it.

  • Extracts the time part of the time or datetime expression and returns it as a string.

    This function is unsafe for statement-based replication. A warning is logged if you use this function when is set to .

  • returns − expressed as a time value. and are time or date-and-time expressions, but both must be of the same type.

    The result returned by is limited to the range allowed for values. Alternatively, you can use either of the functions and , both of which return integers.

  • ,

    With a single argument, this function returns the date or datetime expression as a datetime value. With two arguments, it adds the time expression to the date or datetime expression and returns the result as a datetime value.

  • Adds the integer expression to the date or datetime expression . The unit for is given by the argument, which should be one of the following values: (microseconds), , , , , , , , or .

    The value may be specified using one of keywords as shown, or with a prefix of . For example, and both are legal.

  • Returns − , where and are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part where necessary. The unit for the result (an integer) is given by the argument. The legal values for are the same as those listed in the description of the function.

    Note

    The order of the date or datetime arguments for this function is the opposite of that used with the function when invoked with 2 arguments.

  • This is used like the function, but the string may contain format specifiers only for hours, minutes, seconds, and microseconds. Other specifiers produce a value or .

    If the value contains an hour part that is greater than , the and hour format specifiers produce a value larger than the usual range of . The other hour format specifiers produce the hour value modulo 12.

  • Returns the argument, converted to seconds.

  • Given a date , returns a day number (the number of days since year 0).

    is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable. See Section 12.9, “What Calendar Is Used By MySQL?”, for details.

    Remember that MySQL converts two-digit year values in dates to four-digit form using the rules in Section 11.2, “Date and Time Data Types”. For example, and are seen as identical dates:

    In MySQL, the zero date is defined as , even though this date is itself considered invalid. This means that, for and , returns the values shown here:

    This is true whether or not the SQL server mode is enabled.

  • Given a date or datetime , returns the number of seconds since the year 0. If is not a valid date or datetime value, returns .

    Like , is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable. See Section 12.9, “What Calendar Is Used By MySQL?”, for details.

    Like , , converts two-digit year values in dates to four-digit form using the rules in Section 11.2, “Date and Time Data Types”.

    In MySQL, the zero date is defined as , even though this date is itself considered invalid. This means that, for and , returns the values shown here:

    This is true whether or not the SQL server mode is enabled.

  • If is called with no argument, it returns a Unix timestamp representing seconds since UTC.

    If is called with a argument, it returns the value of the argument as seconds since UTC. The server interprets as a value in the session time zone and converts it to an internal Unix timestamp value in UTC. (Clients can set the session time zone as described in Section 5.1.15, “MySQL Server Time Zone Support”.) The argument may be a , , or string, or a number in , , , or format. If the argument includes a time part, it may optionally include a fractional seconds part.

    The return value is an integer if no argument is given or the argument does not include a fractional seconds part, or if an argument is given that includes a fractional seconds part.

    When the argument is a column, returns the internal timestamp value directly, with no implicit “string-to-Unix-timestamp” conversion.

    The valid range of argument values is the same as for the data type: UTC to UTC. If you pass an out-of-range date to , it returns .

    If you use and to convert between values in a non-UTC time zone and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For example, due to conventions for local time zone changes such as Daylight Saving Time (DST), it is possible for to map two values that are distinct in a non-UTC time zone to the same Unix timestamp value. maps that value back to only one of the original values. Here is an example, using values that are distinct in the time zone:

    If you want to subtract columns, you might want to cast them to signed integers. See Section 12.11, “Cast Functions and Operators”.

  • ,

    Returns the current UTC date as a value in or format, depending on whether the function is used in string or numeric context.

  • ,

    Returns the current UTC time as a value in or format, depending on whether the function is used in string or numeric context.

    If the argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

  • ,

    Returns the current UTC date and time as a value in or format, depending on whether the function is used in string or numeric context.

    If the argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

  • This function returns the week number for . The two-argument form of enables you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from to or from to . If the argument is omitted, the value of the system variable is used. See Section 5.1.8, “Server System Variables”.

    The following table describes how the argument works.

    ModeFirst day of weekRangeWeek 1 is the first week …
    0Sunday0-53with a Sunday in this year
    1Monday0-53with 4 or more days this year
    2Sunday1-53with a Sunday in this year
    3Monday1-53with 4 or more days this year
    4Sunday0-53with 4 or more days this year
    5Monday0-53with a Monday in this year
    6Sunday1-53with 4 or more days this year
    7Monday1-53with a Monday in this year

    For values with a meaning of “with 4 or more days this year,” weeks are numbered according to ISO 8601:1988:

    • If the week containing January 1 has 4 or more days in the new year, it is week 1.

    • Otherwise, it is the last week of the previous year, and the next week is week 1.

    If a date falls in the last week of the previous year, MySQL returns if you do not use , , , or as the optional argument:

    One might argue that should return because the given date actually occurs in the 52nd week of 1999. returns instead so that the return value is “the week number in the given year.” This makes use of the function reliable when combined with other functions that extract a date part from a date.

    If you prefer a result evaluated with respect to the year that contains the first day of the week for the given date, use , , , or as the optional argument.

    Alternatively, use the function:

  • Returns the weekday index for ( = Monday, = Tuesday, … = Sunday).

  • Returns the calendar week of the date as a number in the range from to . is a compatibility function that is equivalent to .

  • Returns the year for , in the range to , or for the “zero” date.

  • ,

    Returns year and week for a date. The year in the result may be different from the year in the date argument for the first and the last week of the year.

    The argument works exactly like the argument to . For the single-argument syntax, a value of 0 is used. Unlike , the value of does not influence .

    The week number is different from what the function would return () for optional arguments or , as then returns the week in the context of the given year.

  • Sours: https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html
    57. DATEDIFF Function in SQL

    In this tutorial, we will study the MySQL function. Suppose you are an HR executive at a company and you have data on the check-in date and time for each employee for today as well as the date they first joined the company in a table. The CEO of the company has tasked you with finding out how many days have elapsed since each employee joined the company.

    Now doing this manually would be a mammoth task. Some employees may have joined more than 5 years ago or so and besides, your CEO wants the exact number of days each employee has been in the company. But we have a computer and we know MySQL, so let us make things easy for ourselves. Let us see how we can use the MySQL function to solve this problem.

    The MySQL function is used to find the difference between two dates or datetime values. In other words, it returns the number of days between two dates. Let us dive deep and take a look at the syntax before we move on to the examples.


    Syntax of MySQL DATEDIFF()

    Where, ‘date1’ and ‘date2’ are two date or datetime expressions.

    Note that DATEDIFF() calculates the differences by subtracting date2 from date1, i.e. MySQL DATEDIFF() computes and returns the value of date1– date2.


    Examples of MySQL DATEDIFF()

    Let us start by looking at a few basic examples. Let us find the number of days between the following –

    • ‘2020-05-31’ and ‘2020-05-01’ ,and
    • ‘2020-06-15’, ‘2020-05-01’.

    We will use the statement and an alias called ‘Number of Days’ to make our output readable. The query is –

    SELECT DATEDIFF('2020-05-31', '2020-05-01') AS 'Number of Days'; SELECT DATEDIFF('2020-06-15', '2020-05-01') AS 'Number of Days';

    And the output is –

    Datediff Basic Example

    MySQL DATEDIFF() With Larger Differences

    can support large differences between the date values, unlike the function. However, make sure you enter valid date values. Let us see a couple of examples where the dates are years apart. Consider the below queries.

    SELECT DATEDIFF('2021-03-01', '2000-02-25') AS 'Number of Days'; SELECT DATEDIFF('2021-01-01', '1999-11-19') AS 'Number of Days';

    And the output is –

    MySQL Datediff Large Values

    DATEDIFF() With Wrong Date Values

    Building on what I said earlier about having valid date values, what if we pass invalid date values? If either of the date in the function is wrong or invalid, then the function returns NULL. Let us see an example of this.

    SELECT DATEDIFF('2020-56-12', '2019-05-15') AS 'Number of Days';

    And the output is –

    MySQL Datediff Wrong Dates

    MySQL DATEDIFF() With Negative Days Difference

    If, by mistake, you pass the second date value as a value larger than the first, you’ll get a negative value for the date difference. This is alright as supports a negative date difference. Let us see an example of this. Consider the below query.

    SELECT DATEDIFF('2000-02-25', '2021-03-01') AS 'Number of Days';

    And the output is –

    Datediff Negative

    DATEDIFF() With CURDATE()

    We can also use the function with the function. Let us find out the number of days between the present day (At the time this article was written, the date was 17th March, 2021) and the date India got independence on August 15, 1947. The query is –

    SELECT DATEDIFF(CURDATE(), '1947-08-15') AS 'Number of Days';

    And the output is –

    Datediff Curdate

    DATEDIFF() With Datetime Values

    As I mentioned in the syntax section, also works with datetime values. However, while computation of the difference between the values, the time value in the datetime value is ignored. Let us see an example of with datetime values.

    SELECT DATEDIFF('2020-05-31 00:00:30', '2020-05-01 23:59:59') AS 'Number of Days';

    And the output is –

    Datediff Datetime

    Working With Tables

    Finally, let us see an example of with tables. Consider the below Employee table.

    Timediff Employee Table

    Now, coming back to the problem I mentioned in the beginning of this article. Suppose you are an HR executive at a company and you have data on the check-in date and time for each employee for today as well as the date they first joined the company in a table. The CEO of the company has tasked you with finding out how many days have elapsed since each employee joined the company.

    Now that we know how to use the function, let us use it to solve the above problem. Our query is –

    SELECT eid, Name, DATEDIFF(CheckInDateTime, Date_Joined) AS 'Number Of Days' FROM Employee;

    And the output is –

    Datediff Table Example

    Conclusion

    is a very important datetime function. Basic subtraction operations are always very important and have abundant use cases. I would encourage you to practice more examples of this function!


    References

    Sours: https://mysqlcode.com/mysql-datediff/

    You will also be interested:

    Database.Guide

    This article looks at the difference between two MySQL functions; and .

    Both functions return the difference between two dates and/or times, but the result is different between the two functions.

    The following table summarizes the difference between these two functions:

    Requires 2 arguments.Requires 3 arguments.
    Subtracts the 2nd argument from the 1st (expr1 − expr2).Subtracts the 2nd argument from the 3rd (expr2 − expr1).
    Result is expressed as a value in days.Result is expressed as the unit provided by the first argument.
    Can compare only the date value of its arguments.Can compare the date and time value of its arguments.

    Example 1 – Basic Operation

    Here’s an example that demonstrates how these functions work, and how the results are different, even when using the same unit.

    SET @date1 = '2010-10-11 00:00:00', @date2 = '2010-10-10 00:00:00'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(day, @date1, @date2) AS 'TIMESTAMPDIFF';

    Result:

    +----------+---------------+ | DATEDIFF | TIMESTAMPDIFF | +----------+---------------+ | 1 | -1 | +----------+---------------+

    So both functions return the difference in days, however one result is positive and the other negative. This is because subtracts the second date from the first, whereas subtracts the first date from the second.

    Example 2 – Changing the Unit

    As the previous example demonstrates, the allows you to specify a unit for the results to be returned as (in fact, it requires you to specify the unit). On the other hand, doesn’t allow you to specify a unit. It only returns the result in days.

    So we could modify the previous example so that returns the number of hours instead of days:

    SET @date1 = '2010-10-11 00:00:00', @date2 = '2010-10-10 00:00:00'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(hour, @date1, @date2) AS 'TIMESTAMPDIFF';

    Result:

    +----------+---------------+ | DATEDIFF | TIMESTAMPDIFF | +----------+---------------+ | 1 | -24 | +----------+---------------+

    You can go all the way to microseconds:

    SET @date1 = '2010-10-11 00:00:00', @date2 = '2010-10-10 00:00:00'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(microsecond, @date1, @date2) AS 'TIMESTAMPDIFF';

    Result:

    +----------+---------------+ | DATEDIFF | TIMESTAMPDIFF | +----------+---------------+ | 1 | -86400000000 | +----------+---------------+

    Example 3 – Precision

    The precision of is one day, and can go down to the microsecond. However the precision of (and the unit that it compares) still depends on the specified unit.

    SET @date1 = '2010-10-10 00:00:00', @date2 = '2010-10-10 23:59:59'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(day, @date1, @date2) AS 'Days', TIMESTAMPDIFF(hour, @date1, @date2) AS 'Hours', TIMESTAMPDIFF(minute, @date1, @date2) AS 'Minutes', TIMESTAMPDIFF(second, @date1, @date2) AS 'Seconds', TIMESTAMPDIFF(microsecond, @date1, @date2) AS 'Microseconds';

    Result:

    +----------+------+-------+---------+---------+--------------+ | DATEDIFF | Days | Hours | Minutes | Seconds | Microseconds | +----------+------+-------+---------+---------+--------------+ | 0 | 0 | 23 | 1439 | 86399 | 86399000000 | +----------+------+-------+---------+---------+--------------+

    And here’s the result if we increment the 2nd date by one second (which brings it to the next day):

    SET @date1 = '2010-10-10 00:00:00', @date2 = '2010-10-11 00:00:00'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(day, @date1, @date2) AS 'Days', TIMESTAMPDIFF(hour, @date1, @date2) AS 'Hours', TIMESTAMPDIFF(minute, @date1, @date2) AS 'Minutes', TIMESTAMPDIFF(second, @date1, @date2) AS 'Seconds', TIMESTAMPDIFF(microsecond, @date1, @date2) AS 'Microseconds';

    Result:

    +----------+------+-------+---------+---------+--------------+ | DATEDIFF | Days | Hours | Minutes | Seconds | Microseconds | +----------+------+-------+---------+---------+--------------+ | -1 | 1 | 24 | 1440 | 86400 | 86400000000 | +----------+------+-------+---------+---------+--------------+

    Here’s another example, this time seeing how it looks when we return months, quarters, and years when the difference is one month (or 31 days):

    SET @date1 = '2010-10-10 00:00:00', @date2 = '2010-11-10 00:00:00'; SELECT DATEDIFF(@date1, @date2) AS 'DATEDIFF', TIMESTAMPDIFF(day, @date1, @date2) AS 'Days', TIMESTAMPDIFF(month, @date1, @date2) AS 'Month', TIMESTAMPDIFF(quarter, @date1, @date2) AS 'Quarter', TIMESTAMPDIFF(year, @date1, @date2) AS 'Year';

    Result:

    +----------+------+-------+---------+------+ | DATEDIFF | Days | Month | Quarter | Year | +----------+------+-------+---------+------+ | -31 | 31 | 1 | 0 | 0 | +----------+------+-------+---------+------+

    Example 4 – Wrong Argument Types

    Both functions return null if they are passed the wrong argument type.

    SET @time1 = '12:15:35', @time2 = '00:00:00'; SELECT DATEDIFF(@time1, @time2) AS 'DATEDIFF', TIMESTAMPDIFF(day, @time1, @time2) AS 'TIMESTAMPDIFF';

    Result:

    +----------+---------------+ | DATEDIFF | TIMESTAMPDIFF | +----------+---------------+ | NULL | NULL | +----------+---------------+

    Example 5 – Mixed Argument Types

    Both functions allow you to provide a date as one argument and a datetime as another argument.

    SET @thedate = '2010-10-11', @thedatetime = '2010-10-10 00:00:00'; SELECT DATEDIFF(@thedate, @thedatetime) AS 'DATEDIFF', TIMESTAMPDIFF(day, @thedate, @thedatetime) AS 'TIMESTAMPDIFF';

    Result:

    +----------+---------------+ | DATEDIFF | TIMESTAMPDIFF | +----------+---------------+ | 1 | -1 | +----------+---------------+

    MySQL, SQLdate functions, dates, functions, mysql

    Sours: https://database.guide/mysql-datediff-vs-timestampdiff-whats-the-difference/


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