The FIRST_DAY function returns a date or timestamp that represents the first day of the month of the argument.

The schema is SYSIBM.

expression

An expression that specifies the datetime value to compute the first day of the month.
The expression must return a value that is a DATE, TIMESTAMP, CHAR, or 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 by using implicit casting.
If expression is a CHAR, VARCHAR, GRAPHIC, or VARGRAPHIC data type, it must be a valid string that is accepted by the TIMESTAMP scalar function.

The result of the function is a timestamp with the same precision as expression, if expression is a timestamp.
Otherwise, the result of the function is a date.
If the argument can be null, the result can be null; if the argument is null, the result is the null value.

Examples

1. Set the host variable FIRST_OF_MONTH with the first day of the current month.

      SET :FIRST_OF_MONTH = FIRST_DAY(CURRENT_DATE)

   The host variable FIRST_OF_MONTH is set with the value representing the beginning of the current month.
   If the current day is 2000-02-10, then FIRST_OF_MONTH is set to 2000-02-01.
2. Set the host variable FIRST_OF_MONTH with the first day of the month in IBM® European standard format for the given date.

      SET :FIRST_OF_MONTH = CHAR(FIRST_DAY(DATE '1965-07-07'), EUR)

   The host variable FIRST_OF_MONTH is set with the value '01.07.1965'.