MySQL has many operators and functions that return a string. This section answers the question: What is the character set and collation of such a string?
For simple functions that take string input and return a string result as output, the output’s character set and collation are the same as those of the principal input value. For example, UPPER(X) returns a string whose character string and collation are the same as that of X. The same applies for INSTR(), LCASE(), LOWER(), LTRIM(), MID(), REPEAT(), REPLACE(), REVERSE(), RIGHT(), RPAD(), RTRIM(), SOUNDEX(), SUBSTRING(), TRIM(), UCASE(), and UPPER(). Note: The REPLACE() function, unlike all other functions, always ignores the collation of the string input and performs a case-sensitive comparison. If a string input or function result is a binary string, the string has no character set or collation.
