The THIS_MONTH function returns the first day of the month in the specified date.

The schema is SYSIBM.

datetime-expression

An expression that specifies a date for which first day of the month is to be returned.
The expression must return a value that is a DATE, a TIMESTAMP, a CHAR, or a VARCHAR data type.
In a Unicode database, the expression can also be a GRAPHIC or VARGRAPHIC data type.
CHAR, VARCHAR, GRAPHIC, and VARGRAPHIC are supported using implicit casting.
If datetime-expression is a CHAR, VARCHAR, GRAPHIC, or VARGRAPHIC data type, it must be a valid string accepted by the TIMESTAMP scalar function.

The result of the function is DATE.
If the argument can be null, the result can be null. If the argument is null, the result is the null value.

Example

Returns the date value of the first day of the month specified by the input.

      values this_month('2007-02-18')
      Result: 2007-02-01