DROP TABLE IF EXISTS `table`;
CREATE TABLE `table` (
`id` tinyint(3) unsigned NOT NULL AUTO_INCREMENT,
`text` text COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
INSERT INTO `table` VALUES ('1', 'Unpacked reserved sir offering bed judgment may and quitting speaking. Is do be improved raptures offering required in replying raillery. Stairs ladies friend by in mutual an no. Mr hence chief he cause. Whole no doors on hoped. Mile tell if help they ye full name. \r\n\r\nLadyship it daughter securing procured or am moreover mr. Put sir she exercise vicinity cheerful wondered. Continual say suspicion provision you neglected sir curiosity unwilling. Simplicity end themselves increasing led day sympathize yet. General windows effects not are drawing man garrets. Common indeed garden you his ladies out yet. Preference imprudence contrasted to remarkably in on. Taken now you him trees tears any. Her object giving end sister except oppose. \r\n\r\nWas justice improve age article between. No projection as up preference reasonably delightful celebrated. Preserved and abilities assurance tolerably breakfast use saw. And painted letters forming far village elderly compact. Her rest west each spot his and you knew. Estate gay wooded depart six far her. Of we be have it lose gate bred. Do separate removing or expenses in. Had covered but evident chapter matters anxious.');
INSERT INTO `table` VALUES ('2', 'Unpacked reserved sir offering bed judgment may and quitting speaking. Is do be improved raptures offering required in replying raillery. Stairs ladies friend by in mutual an no. Mr hence chief he cause. Whole no doors on hoped. Mile tell if help they ye full name. \r\n\r\nLadyship it daughter securing procured or am moreover mr. Put sir she exercise vicinity cheerful wondered. Continual say suspicion provision you neglected sir curiosity unwilling. Simplicity end themselves increasing led day sympathize yet. General windows effects not are drawing man garrets. Common indeed garden you his ladies out yet. Preference imprudence contrasted to remarkably in on. Taken now you him trees tears any. Her object giving end sister except oppose. \r\n\r\nWas justice improve age article between. No projection as up preference reasonably delightful celebrated. Preserved and abilities assurance tolerably breakfast use saw. And painted letters forming far village elderly compact. Her rest west each spot his and you knew. Estate gay wooded depart six far her. Of we be have it lose gate bred. Do separate removing or expenses in. Had covered but evident chapter matters anxious');
GROUP BY
結果セットを使用せずにクエリを実行するGROUP_CONCAT()
と、期待どおりになります ( の各バリエーションに 1 つずつ、2 つの行が表示されますtext
)。
SELECT
`text`
FROM
`table`
GROUP BY
`text`;
+-----------------------------------+
| text |
+-----------------------------------+
| Unpacked reserved sir offering... |
| Unpacked reserved sir offering... |
+-----------------------------------+
2 rows in set (0.02 sec)
ただし、結果セットを使用して同じクエリを実行すると、GROUP_CONCAT()
期待どおりになりません (2 つのフィールドの連結された文字列を含む 1 つの行が表示されid
ます)。
SELECT
GROUP_CONCAT(`id` SEPARATOR ', ') AS ids
FROM
`table`
GROUP BY
`text`;
+------+
| ids |
+------+
| 1, 2 |
+------+
1 row in set (0.00 sec)
私の質問:
GROUP_CONCAT()
usingが返される行数に影響するのはなぜですか?
私の最初の仮定はGROUP_CONCAT_MAX_LEN
、それと関係があるということでした (私の場合は 1024 に設定されています) が、それは にのみ影響しGROUP_CONCAT()
、影響しませんGROUP BY
(また、お気づきかもしれませんが、私はフィールドではなくフィールドで使用GROUP_CONCAT()
しており、その結果を超えることさえありません)。id
text
GROUP_CONCAT_MAX_LEN