Basic Language Elements › Basic Operations (Assignment and Comparison)

Basic Operations (Assignment and Comparison)

The basic operations of the SQL language are assignment and comparison.

Assignment operations are performed during the execution of:

• INSERT
• UPDATE
• FETCH

Comparison operations are performed during the execution of statements that include predicates and other language elements such as:

• DISTINCT
• GROUP BY
• MAX
• MIN
• ORDER BY

The basic rule for both operations is that numbers and strings are not compatible. This means that:

• Numbers and strings cannot be compared.
• Numbers cannot be assigned to string columns or variables.
• Strings cannot be assigned to numeric columns or variables.

All character strings are compatible. For example one character string can be compared to another character string.

All numbers are compatible. (See Numeric Assignments and Numeric Comparisons for information on conversions made during assignment and comparison operations.)