Usage of mysql string functions CONCAT_WS and CONCAT ()

This article will introduce in detail the usage of mysql string functions CONCAT_WS and CONCAT (). If you need to know the usage and difference of these two functions, you can refer.

CONCAT (str1, str2 ,...)

Method
CONCAT (str1, str2 ,...)

Description
Returns the string generated by the connection parameter. If any parameter is NULL, the return value is NULL. If all parameters are non-binary strings, the result is a non-binary string. If the independent variable contains any binary string, the result is a binary string. A numeric parameter is converted to an equivalent binary string format. To avoid this, you can use an explicit cast, for example: select concat (CAST (int_col as char ), char_col ).

Example

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Mysql> select concat ('exam', 'ple '); + -------- + | CONCAT ('expam', 'ple ') | + -------- + | Example | + -------- + 1 row in set (0.00 sec) Mysql> SELECT CONCAT_WS ('', 'catch ', 'A', 'falling', 'star '); + ----------------- + | CONCAT_WS ('', 'catch ', 'A', 'falling', 'star') | + ----------------- + | Catch a falling star | + ----------------- + 1 row in set (0.00 sec) Mysql> select concat ('My, NULL, 'ql '); -> NULL Mysql> select concat (14.3 ); -> '14. 3 ′

CONCAT_WS (separator, str1, str2 ,...)

Method
CONCAT_WS (separator, str1, str2 ,...)

Description
CONCAT_WS () represents CONCAT With Separator, which is a special form of CONCAT. The first parameter is the delimiter of other parameters. The separator is placed between the two strings to be connected. The delimiter can be a string or another parameter. If the Delimiter is NULL, the result is NULL. The function ignores the NULL value after any separator parameter.

Example

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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'

Note: CONCAT_WS () does not ignore any null strings. (However, all NULL values are ignored ).