The LOCATE function is used to search for a string within another string. If the desired string is found, LOCATE returns the index at which it is found. If the desired string is not found, LOCATE returns 0.
LOCATE(CharacterExpression, CharacterExpression [, StartPosition] )
The return type for LOCATE is an integer. The LOCATE function returns an integer indicating the index position within the second argument at which the first argument was first located. Index positions start with 1. If the first argument is not found in the second argument, LOCATE returns 0. If the first argument is an empty string (''), LOCATE returns the value of the third argument (or 1 if it was not provided), even if the second argument is also an empty string. If a NULL value is passed for either of the CharacterExpression arguments, NULL is returned.
-- returns 2, since 'love' is found at index position 2: VALUES LOCATE('love', 'clover')
-- returns 0, since 'stove' is not found in 'clover': VALUES LOCATE('stove', 'clover')
-- returns 5 (note the start position is 4): VALUES LOCATE('iss', 'Mississippi', 4)
-- returns 1, because the empty string is a special case: VALUES LOCATE('', 'ABC')
-- returns 0, because 'AAA' is not found in '': VALUES LOCATE('AAA', '')
-- returns 3 VALUES LOCATE('', '', 3)