mysql group_concat method example to write group fields into one row

This article uses an example to describe how to use MySQL group_concat to write grouped fields into one row. Share with you for your reference, the details are as follows:

Function : Connect the values ​​in the same group generated by group by and return a string result.

Function syntax :

group_concat( [DISTINCT] Fields to be connected [Order BY Sorting fields ASC/DESC] [Separator 'Separator'] )

Example

Query the article list and use multiple tags of the same article as one field

Tag table structure

CREATE TABLE `book_tag` (
 `id` int(10) NOT NULL AUTO_INCREMENT,
 `tag_name` varchar(255) NOT NULL DEFAULT '0' COMMENT 'Tag name',
 `tag_nums` int(10) NOT NULL DEFAULT '0' COMMENT 'Number of references',
 PRIMARY KEY (`id`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

Tag article relationship table

CREATE TABLE `book_tag_book` (
 `id` int(10) NOT NULL AUTO_INCREMENT,
 `book_id` int(10) NOT NULL DEFAULT '0' COMMENT 'Book id',
 `tag_id` int(10) NOT NULL DEFAULT '0' COMMENT 'Tag ID',
 PRIMARY KEY (`id`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

Query

SELECT
 `b`.`id`,
 `b`.`book_name`,
 `b`.`book_flash`,
 `b`.`introduction`,
 GROUP_CONCAT(a.tag_name)
FROM
 `book_book` `b`
LEFT JOIN `book_tag_book` `t` ON `t`.`book_id` = `b`.`id`
LEFT JOIN `book_tag` `a` ON `a`.`id` = `t`.`tag_id`
GROUP BY b.id

result

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