Character functions : accept character input and return both character and number values. Types of character function are :
Case-Manipulation Functions : LOWER, UPPER, INITCAP
Character-Manipulation Functions : CONCAT, SUBSTR, LENGTH, INSTR, LPAD/RPAD, TRIM, REPLACE
Number Functions : accept Numeric input and return numeric values. Number Functions are: ROUND, TRUNC, and MOD
Date Functions : operates on values of the Date data type. (All date functions return a value of DATE data type except the MONTHS_BETWEEN Function, which returns a number. Date Functions are MONTHS_BETWEEN, ADD_MONTHS, NEXT_DAY, LAST_DAY, ROUND, TRUNC.
