HOUR scalar function

The HOUR function returns the hour part of a value.

The schema is SYSIBM.

The argument must be an expression that returns a value of one of the following built-in data types: a time, a timestamp, a character string, a graphic string, or a numeric data type.

If expression is a character or graphic string, it must not be a CLOB or DBCLOB, and its value must be a valid string representation of a time or timestamp with an actual length of not greater than 255 bytes. For the valid formats of string representations of times and timestamps, see String representations of datetime values.
If expression is a number, it must be a time or timestamp duration. For the valid formats of time and timestamp durations, see Datetime operands.

If expression is a timestamp with a time zone, or a valid string representation of a timestamp with a time zone, the result is determined from the UTC representation of the datetime value.

The result of the function is a large integer.

The result can be null; if the argument is null, the result is the null value.

The other rules depend on the data type of the argument:

If the argument is a time, timestamp, or string representation of either, the result is the hour part of the value, which is an integer in the range 1–24.
If the argument is a time duration or timestamp duration, the result is the hour part of the value, which is an integer between -99 and +99. A nonzero result has the same sign as the argument.
If the argument contains a time zone, the result is the hour part of the value expressed in UTC.

Example 1: Assume that a table named CLASSES contains a row for each scheduled class. Also assume that the class starting times are in a TIME column named STARTTM. Select those rows in CLASSES that represent classes that start after the noon hour.

   SELECT *
     FROM CLASSES
     WHERE HOUR(STARTTM) > 12;

Example 2: The following invocations of the HOUR function returns the same result:

SELECT HOUR('2003-01-02-20.00.00'), 
			HOUR('2003-01-02-12.00.00-08:00'), 
			HOUR('2003-01-03-05.00.00+09:00') 
		FROM SYSIBM.SYSDUMMY1;

For each invocation of the HOUR function in this SELECT statement, the result is 20.

When the input argument contains a time zone, the result is determined from the UTC representation of the input value. The string representations of a timestamp with a time zone in the SELECT statement all have the same UTC representation: 2003-01-02-20.00.00.