GROUP_CONCAT

Function Description

The GROUP_CONCAT function returns a string that joins content specified by a column or expression.

If the result set does not have any rows, this function returns NULL.

Function Syntax

> GROUP_CONCAT(expr)

The complete syntax is as follows:

GROUP_CONCAT([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [SEPARATOR str_val])

Parameter definition

Parameters	Description
expr	Required parameters. It specifies one or more columns or expressions to join.
DISTINCT	Optional parameters. It is used to eliminate duplicate values.
ORDER BY	Optional parameters. It is used to sort the content to be connected. By default, it sorts the values ​​in ascending order. If you want to sort the values ​​in descending order, you need to specify the DESC option explicitly.
SEPARATOR	Optional parameters. Connector. The default is ,.

Return value

The return value is a non-binary or binary string, depending on whether the parameter expr is a non-binary or binary string.

If the result set does not have any rows, this function returns NULL.

Example

create table t1(a int,b text,c text);
insert into t1 values(1,"a","bc"),(2,"ab","c"),(3,"aa","bb"),(3,"aa","bb");

mysql> select group_concat(distinct a,b,c separator '|') from t1;
+------------------------------------------+
| group_concat(distinct a, b, c, |) |
+------------------------------------------+
| 1abc|2abc|3aabb|
+------------------------------------------+
1 row in set (0.01 sec)

mysql> select group_concat(distinct b,c separator '|') from t1 group by a;
+------------------------------------+
| group_concat(distinct b, c, |) |
+------------------------------------+
| abc |
| abc |
| aabb |
+------------------------------------+
3 rows in set (0.01 sec)

mysql> select group_concat(distinct b,c separator '|') from t1;
+------------------------------------+
| group_concat(distinct b, c, |) |
+------------------------------------+
| abc|abc|aabb|
+------------------------------------+
1 row in set (0.01 sec)