Concatenating multiple mysql fields _ MySQL

The following two functions can be used to concatenate the query result line fields of Mysql: 1concat function mysqlselectconcat (39; 139;, 39; 239;, 39; 339;) fromtest; + --------------------- + | concat (39; 139;, 39; 2 concatenate the query result line fields of Mysql, which can be implemented using the following two functions:

1. concat function

mysql> select concat('1','2','3') from test ;+---------------------+| concat('1','2','3') |+---------------------+| 123 |+---------------------+

If NULL exists in the connection string, the returned result is NULL:

mysql> select concat('1','2',NULL,'3') from test ;+--------------------------+| concat('1','2',NULL,'3') |+--------------------------+| NULL |+--------------------------+

2. concat_ws function

Concat (separator, str1, str2,...) 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.

mysql> select concat_ws(':','1','2','3') from test ;+----------------------------+| concat_ws(':','1','2','3') |+----------------------------+| 1:2:3 |+----------------------------+

If the delimiter is NULL, the returned result is NULL:

mysql> select concat_ws(NULL,'1','2','3') from test; +-----------------------------+| concat_ws(NULL,'1','2','3') |+-----------------------------+| NULL | +-----------------------------+

If NULL exists in the parameter, it will be ignored:

mysql> select concat_ws(':','1','2',NULL,NULL,NULL,'3') from test ;+-------------------------------------------+| concat_ws(':','1','2',NULL,NULL,NULL,'3') |+-------------------------------------------+| 1:2:3 |+-------------------------------------------+

NULL can be judged and replaced with other values.

mysql>  select concat_ws(':','1','2',ifNULL(NULL,'0'),'3') from bank limit 1;  +---------------------------------------------+| concat_ws(':','1','2',ifNULL(NULL,'0'),'3') |+---------------------------------------------+| 1:2:0:3                                     | +---------------------------------------------+