GROUP_CONCAT

Description

The GROUP_CONCAT function concatenates multiple rows of results in the result set into a string.

Syntax

GROUP_CONCAT([DISTINCT] <str>[, <sep>] [ORDER BY { <col_name> | <expr>} [ASC | DESC]])

Parameters

Parameters	Description
<str>	Required. The expression of the value to be concatenated.
<sep>	Optional. The separator between strings.
<col_name>	Optional. The column used for sorting.
<expr>	Optional. The expression used for sorting.

Return Value

Returns a value of type VARCHAR. If the input data contains NULL, returns NULL.

Example

-- setup
create table test(
    value varchar(10)
) distributed by hash(value) buckets 1
properties ("replication_num"="1");

insert into test values
    ("a"),
    ("b"),
    ("c"),
    ("c");

select GROUP_CONCAT(value) from test;

+-----------------------+
| GROUP_CONCAT(`value`) |
+-----------------------+
| a, b, c, c            |
+-----------------------+

select GROUP_CONCAT(DISTINCT value) from test;

+-----------------------+
| GROUP_CONCAT(`value`) |
+-----------------------+
| a, b, c               |
+-----------------------+

select GROUP_CONCAT(value ORDER BY value DESC) from test;

+-----------------------+
| GROUP_CONCAT(`value`) |
+-----------------------+
| c, c, b, a            |
+-----------------------+

select GROUP_CONCAT(DISTINCT value ORDER BY value DESC) from test;

+-----------------------+
| GROUP_CONCAT(`value`) |
+-----------------------+
| c, b, a               |
+-----------------------+

select GROUP_CONCAT(value, " ") from test;

+----------------------------+
| GROUP_CONCAT(`value`, ' ') |
+----------------------------+
| a b c c                    |
+----------------------------+

select GROUP_CONCAT(value, NULL) from test;

+----------------------------+
| GROUP_CONCAT(`value`, NULL)|
+----------------------------+
| NULL                       |
+----------------------------+