Date and Time Functions - SQL Server to Aurora PostgreSQL Migration Playbook
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Date and Time Functions

Feature compatibility Amazon SCT / Amazon DMS automation level Amazon SCT action code index Key differences


                              Four star feature compatibility


                              Four star automation level

Data Types

PostgreSQL is using different function names.

SQL Server Usage

Date and Time Functions are scalar functions that perform operations on temporal or numeric input and return temporal or numeric values.

System date and time values are derived from the operating system of the server on which SQL Server is running.

This section doesn’t address time zone considerations and time zone aware functions. For more information about time zone handling, see Data Types.

Syntax and Examples

The following table includes the most commonly used date and time functions.

Function Purpose Example Result Comments

GETDATE and GETUTCDATE

Return a datetime value that contains the current local or UTC date and time.

SELECT GETDATE()

2018-04-05 15:53:01.380

DATEPART, DAY, MONTH, and YEAR

Return an integer value representing the specified DATEPART of a specified date.

SELECT MONTH(GETDATE()), YEAR(GETDATE())

4, 2018

DATEDIFF

Returns an integer value of DATEPART boundaries that are crossed between two dates.

SELECT DATEDIFF(DAY, GETDATE(), EOMONTH(GETDATE()))

25

How many days left until end of the month.

DATEADD

Returns a datetime value that is calculated with an offset interval to the specified DATEPART of a date.

SELECT DATEADD(DAY, 25, GETDATE())

2018-04-30 15:55:52.147

CAST and CONVERT

Converts datetime values to and from string literals and to and from other datetime formats.

SELECT CAST (GETDATE() AS DATE) SELECT CONVERT (VARCHAR(20), GETDATE(), 112)

2018-04-05 20180405

Default date format. Style 112 (ISO) with no separtors.

For more information, see Date and Time functions in the SQL Server documentation.

PostgreSQL Usage

Amazon Aurora PostgreSQL-Compatible Edition (Aurora PostgreSQL) provides a very rich set of scalar date and time functions; more than SQL Server.

While some of the functions appear to be similar to those in SQL Server, the functionality is significantly different. Take extra care when migrating temporal logic to Aurora PostgreSQL paradigms.

Functions and Definition

PostgreSQL function Function definition

AGE

Subtract from current_date.

CLOCK_TIMESTAMP

Current date and time.

CURRENT_DATE

Current date.

CURRENT_TIME

Current time of day.

CURRENT_TIMESTAMP

Current date and time (start of current transaction).

DATE_PART

Get subfield (equivalent to extract).

DATE_TRUNC

Truncate to specified precision.

EXTRACT

Get subfield.

ISFINITE

Test for finite interval.

JUSTIFY_DAYS

Adjust interval so 30-day time periods are represented as months.

JUSTIFY_HOURS

Adjust interval so 24-hour time periods are represented as days.

JUSTIFY_INTERVAL

Adjust interval using justify_days and justify_hours, with additional sign adjustments.

LOCALTIME

Current time of day.

MAKE_DATE

Create date from year, month and day fields.

MAKE_INTERVAL

Create interval from years, months, weeks, days, hours, minutes and seconds fields.

MAKE_TIME

Create time from hour, minute and seconds fields.

MAKE_TIMESTAMP

Create timestamp from year, month, day, hour, minute, and seconds fields.

MAKE_TIMESTAMPTZ

Create timestamp with time zone from year, month, day, hour, minute, and seconds fields. If the time zone isn’t specified, the current time zone is used.

NOW

Current date and time.

STATEMENT_TIMESTAMP

Current date and time.

TIMEOFDAY

Current date and time (like clock_timestamp, but as a text string).

TRANSACTION_TIMESTAMP

Current date and time.

TO_TIMESTAMP

Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to timestamp.

Summary

SQL Server function Aurora PostgreSQL function

GETDATE, CURRENT_TIMESTAMP

NOW, CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP

GETUTCDATE

current_timestamp at time zone 'utc'

DAY, MONTH, and YEAR

EXTRACT(DAY/MONTH/YEAR FROM TIMESTAMP timestamp_value)

DATEPART

EXTRACT, DATE_PART

DATEDIFF

DATE_PART

DATEADD

+ INTERVAL 'X days/months/years'

CAST and CONVERT

CAST

For more information, see Date/Time Functions and Operators in the PostgreSQL documentation.