String Function , Number Function , Date and Time Function, General Function

String Functions

Manipulate text values — e.g. UPPER(), LOWER(), LENGTH(), SUBSTR(), TRIM(), and CONCAT() (or the || operator).

Number Functions

Perform mathematical operations — e.g. ROUND(), TRUNC(), MOD(), ABS(), and POWER().

Date and Time Functions

Work with date/time values — e.g. SYSDATE, ADD_MONTHS(), MONTHS_BETWEEN(), and TO_CHAR() for formatting a date as text.

General Functions

Handle conditional or null-related logic — e.g. NVL() (substitutes a value when NULL), DECODE(), and CASE expressions.

Why Testers Use These

These functions let testers write precise verification queries — for instance, formatting a date to compare it against a UI display, or trimming whitespace before comparing string values pulled from the database.