concat usage of MySQL

question: Fuzzy query in MyBatis Mapper file:

The MySQL CONCAT () function is used to concatenate multiple strings into a single string, one of the most important MySQL functions, and the MySQL CONCAT () function is described in detail below for your reference

MySQL CONCAT (str1,str2,...)
Returns the string that results from the connection parameter. If any one of the arguments is NULL, the return value is null. There may be one or more parameters. If all parameters are non-binary strings, the result is a non-binary string. If the argument contains any twos binary string, the result is a binary string. A numeric parameter is converted to the equivalent binary string format; To avoid this, you can use explicit type cast, for example: SELECT CONCAT (CAST (Int_col as CHAR), Char_col)

mysql> SELECT CONCAT (' My ', ' S ', ' QL ');

' MySQL '

mysql> SELECT CONCAT (' My ', NULL, ' QL ');

, NULL

Mysql> SELECT CONCAT (14.3);

' 14.3′

MySQL Concat_ws (separator,str1,str2,...)
Concat_ws () represents CONCAT with Separator, which is a special form of the CONCAT (). The first parameter is the delimiter for the other parameter. The position of the delimiter is placed between the two strings to be concatenated. The delimiter can be a string, or it can be another parameter. If the delimiter is null, the result is null. The function ignores NULL values after any delimiter parameters.

mysql> SELECT concat_ws (', ', ' First name ', ' Second name ', ' last Name ');

' First Name,second name,last name '

mysql> SELECT concat_ws (', ', ' First name ', NULL, ' last Name ');

' First name,last name '

MySQL Concat_ws () does not ignore any empty strings. (All NULL is ignored, however).

concat usage of MySQL