MySQL の GROUP_CONCAT

SELECT GROUPING_COLUMN,
       GROUP_CONCAT(COLUMN_NAME ORDER BY COLUMN_NAME SEPARATOR 'SEPARATOR_TEXT')
FROM TABLE_NAME
GROUP BY GROUPING_COLUMN;

SELECT rating, GROUP_CONCAT(title ORDER BY title SEPARATOR ', ') AS titles
FROM film
WHERE length = 185
GROUP BY rating
ORDER BY rating;

+--------+--------------------------------------------------+
| rating | titles                                           |
+--------+--------------------------------------------------+
| G      | CONTROL ANTHEM, DARN FORRESTER, MUSCLE BRIGHT    |
| PG     | WORST BANGER                                     |
| PG-13  | CHICAGO NORTH, GANGS PRIDE, POND SEATTLE         |
| R      | HOME PITY, SOLDIERS EVOLUTION, SWEET BROTHERHOOD |
+--------+--------------------------------------------------+
4 rows in set (0.00 sec)

SELECT rating, GROUP_CONCAT(DISTINCT rental_rate ORDER BY rental_rate) AS rates
FROM film
GROUP BY rating
ORDER BY rating;

+--------+----------------+
| rating | rates          |
+--------+----------------+
| G      | 0.99,2.99,4.99 |
| PG     | 0.99,2.99,4.99 |
| PG-13  | 0.99,2.99,4.99 |
| R      | 0.99,2.99,4.99 |
| NC-17  | 0.99,2.99,4.99 |
+--------+----------------+
5 rows in set (0.00 sec)

SELECT LENGTH(GROUP_CONCAT(title)) AS bytes FROM film;

+-------+
| bytes |
+-------+
|  1024 |
+-------+
1 row in set, 1 warning (0.00 sec)

SELECT @@group_concat_max_len AS max_len;

+---------+
| max_len |
+---------+
|    1024 |
+---------+
1 row in set (0.00 sec)