4. Understanding the Elements of SQL Statements : SQL Operations : Arithmetic Operations : Date and Time Arithmetic
 
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Date and Time Arithmetic
The following arithmetic is supported for date and time data types.
Note:  Notes:
• INGRESDATE can store both absolute values and interval values.
• "interval type" can be any of the ANSI forms or the INGRESDATE interval form
• "absolute type" is a non-interval form
Operators that return absolute date forms:
absolute type
-
interval type
=
absolute type
absolute type
+
interval type
=
absolute type
interval type
+
absolute type
=
absolute type
The combining rules are: If either term is INGRESDATE, the result will also be INGRESDATE; otherwise, the result will be the same as the absolute term.
Operators used with intervals:
- interval type
=
interval type
 
 
+ interval type
=
interval type
 
 
absolute type
-
absolute type
=
interval type
interval type
+
interval type
=
interval type
interval type
-
interval type
=
interval type
interval type
*
numeric-expression
=
interval type
numeric-expression
*
interval type
=
interval type
interval type
/
numeric-expression
=
interval type
interval type
/
interval type
=
numeric-expression
The combining rules are:
• ANSI absolute types must match to take their difference.
• You cannot combine ANSI Year To Month and ANSI Day To Second intervals.
• If an operand is INGRESDATE the result will also be INGRESDATE.