SQLite’s DATE() function provides us with the ability to return the date of the first instance of a given day of a given month. Therefore, we can use it to return the first Monday of a given month. We can also use it to return the first Tuesday, Wednesday, Thursday, Friday, etc.
We can use DATETIME() if we want a datetime value to be returned.
If you have a Unix timestamp, you can use SQLite’s DATETIME() function with the unixepoch modifier to compute the actual date and time.
You can alternatively use the DATE() function if you only need the date to be returned. And it’s also possible to use the TIME() function to return just the time portion.
In PostgreSQL, we can use the + operator to add one or more months to a date. There are several options when it comes to specifying the actual number of months.
In SQLite, we can use the following method to calculate the last day of a given month.
We can base this either on the current date, or on some other specific date.
Continue readingSQLite gives us the ability to return the date of the beginning of the month, based on a given date.
This means we can return the date of the first day of the current month, or the first day of the month based on a date that we specify.
This allows us to perform further calculations on the resulting date, like adding a given number of days to it.
Continue readingIn SQLite, we can use the DATE() function to subtract one or more years from a date.
For datetime values, we can use the DATETIME() function.
The + operator allows us to add one or more days to a given date in PostgreSQL. We have a few options when it comes to specifying the actual number of days.
SQLite doesn’t have a DATEADD() function like SQL Server (or an ADDDATE() or ADD_DATE() function like in some other DBMSs), but it does have the DATE() function that can make additions to a date value.
SQLite also has a DATETIME() function that can make additions to a datetime value (as well as a TIME() function for time values).
We can subtract one or more days from a date in PostgreSQL with the - operator.
Updated 20 April 2024 to include the date_add() function.
SQL Server has its DATEADD() function that adds an interval to a date value. MySQL’s DATE_ADD() and ADDDATE() for does the same thing, as does MariaDB’s DATE_ADD() and ADDDATE(). SQLite has a DATE() function that also provides the option of adding an interval to a given date.
Prior to version 16, PostgreSQL didn’t have a DATEADD() or equivalent function. But with PostgreSQL 16 came with the introduction of the date_add() function, which allows us to add an interval to a timestamp with time zone.
We can also add and subtract values from dates with date/time operators such as + and -.