Syntax
CONCAT_WS(separator, str1, .., strN)
Purpose
The CONCAT_WS function concatenates multiple strings into one string, with the separator used to separate adjacent strings. If a parameter is NULL, it is ignored.
This function does not ignore empty strings.
Examples
obclient> SELECT
CONCAT_WS('_', 'First', 'Second'),
CONCAT_WS('_', 'First', NULL, 'Second')
\G
*************************** 1. row ***************************
CONCAT_WS('_', 'First', 'Second'): First_Second
CONCAT_WS('_', 'First', NULL, 'Second'): First_Second
1 row in set