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group_concat

Description

This is an aggregate function similar to sum(). group_concat concatenates non-null values into one string, with the second argument sep being the separator. The second argument can also be omitted. This function usually needs to be used along with group by.

Please note that strings may not be concatenated in sequence because it uses distributed computing.

Syntax

VARCHAR group_concat(VARCHAR str[, VARCHAR sep])

Parameters

  • str: the values to concatenate. It must evaluate to VARCHAR.
  • sep: the separator, optional. If it is not specified, a comma and a space (, ) is used by default.

Return value

Returns a VARCHAR value.

Examples

CREATE TABLE IF NOT EXISTS group_concat (
    id        tinyint(4)      NULL,
    value   varchar(65533)  NULL
) ENGINE=OLAP
DISTRIBUTED BY HASH(id);

INSERT INTO group_concat VALUES
(1,'fruit'),
(2,'drinks'),
(3,null),
(4,'fruit'),
(5,'meat'),
(6,'seafood');

select * from group_concat order by id;
+------+---------+
| id   | value   |
+------+---------+
|    1 | fruit   |
|    2 | drinks  |
|    3 | NULL    |
|    4 | fruit   |
|    5 | meat    |
|    6 | seafood |
select group_concat(value) from group_concat;
+-------------------------------------+
| group_concat(value)                 |
+-------------------------------------+
| meat, fruit, seafood, fruit, drinks |
+-------------------------------------+

MySQL > select group_concat(value, " ") from group_concat;
+---------------------------------+
| group_concat(value, ' ')        |
+---------------------------------+
| fruit meat fruit drinks seafood |
+---------------------------------+

keyword

GROUP_CONCAT,GROUP,CONCAT

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