CONCAT returns a string that is a concatenation of its arguments. For example,

SELECT a FROM Address a WHERE CONCAT(a.postCode, a.country)
LIKE 'M%UK'

SUBSTRING returns a portion of a string which is supplied as an argument to the function. The first argument is the input string, the second argument is an integer indicating the starting position of the substring, and the third argument is the length of the substring. The first position of the string is denoted by 1. For example,

SELECT a FROM Address a WHERE SUBSTRING(a.postCode, 1, 3)
= 'RC3'

TRIM trims a specified character from a string. The syntax of the TRIM function is

TRIM ([TRIM_SPECIFICATION] [TRIM_CHARACTER] FROM INPUT_STRING)

The trim specification takes one of the values LEADING, TRAILING, or BOTH. BOTH is the default. The default trim character is a space (or blank). For example, the query

SELECT a...