Understanding CONCAT() and Why || Does Not Work for String Concatenation in MySQL
The CONCAT() function in MySQL is used to join (concatenate) two or more strings into one. It is the standard and recommended way to perform string concatenation in MySQL.
CONCAT(str1, str2, ...) joins multiple strings together into a single result.
It accepts any number of arguments.
If any argument is NULL, the entire result becomes NULL.
In many SQL databases (like Oracle, PostgreSQL),
||is used as a string concatenation operator.But in MySQL,
||is NOT a string concatenation operator.MySQL treats
||as a logical OR operator, not a concatenation operator.So using
||will return 0 or 1 (true or false), not combined strings.
||is part of the ANSI SQL standard for OR.MySQL follows that rule and keeps
||as a logical operator.Therefore, only CONCAT() (or CONCAT_WS) can be used for string joining.
In summary, CONCAT() is the correct function for joining strings in MySQL, while || performs logical OR and cannot be used for concatenation.