[英]mysql group_concat on multiple tables
這是我第一次使用stackoverflow,...對我溫柔;)
在地圖表上使用多個JOIN時,我從GROUP_CONCAT獲取重復結果時遇到的問題很少。
解釋這個並不容易,但我會嘗試:
我創建了一個用於測試的SQLFiddle: http ://sqlfiddle.com/#!9 / d2b347 / 3
對於所有帖子,我希望查詢只是一個而不是1,然后對每個測試進行錘擊。 但是由於GROUP_CONCAT正在合並這些測試結果,我得到的數據是我想要的兩倍。
有可能以某種方式使查詢更可靠。 要始終將GROUP_CONCAT作為確切的測試次數?
我希望/希望輸出為:
|---------|-----------------|------------|---------|-------------|
| post_id | flows | flow_types | powers | power_types |
|---------|-----------------|------------|---------|-------------|
| 1 | 100,140 | a,b | 1,1 | a,b |
|---------|-----------------|------------|---------|-------------|
| 2 | 200,200,200 | a,b,c | (null) | (null) |
|---------|-----------------|------------|---------|-------------|
但它是:
|---------|-----------------|------------|---------|-------------|
| post_id | flows | flow_types | powers | power_types |
|---------|-----------------|------------|---------|-------------|
| 1 | 100,100,140,140 | a,a,b,b | 1,1,1,1 | a,b,a,b |
|---------|-----------------|------------|---------|-------------|
| 2 | 200,200,200 | a,b,c | (null) | (null) |
|---------|-----------------|------------|---------|-------------|
和GROUP_CONCAT DISTINCT我得到:
|---------|-----------------|------------|---------|-------------|
| post_id | flows | flow_types | powers | power_types |
|---------|-----------------|------------|---------|-------------|
| 1 | 100,140 | a,b | 1 | a,b |
|---------|-----------------|------------|---------|-------------|
| 2 | 200 | a,b,c | (null) | (null) |
|---------|-----------------|------------|---------|-------------|
這是創建查詢:
DROP TABLE IF EXISTS `posts`;
CREATE TABLE IF NOT EXISTS `posts` (
`post_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`post` varchar(256) CHARACTER SET ascii NOT NULL,
PRIMARY KEY (`post_id`),
UNIQUE KEY `UNQ_post` (`post`) USING HASH
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `posts_test1`;
CREATE TABLE IF NOT EXISTS `posts_test1` (
`post_id` bigint(20) unsigned NOT NULL,
`test1_id` bigint(20) unsigned NOT NULL,
`type_id` int(10) unsigned NOT NULL DEFAULT 1,
PRIMARY KEY (`post_id`,`test1_id`,`type_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test1`;
CREATE TABLE IF NOT EXISTS `test1` (
`test1_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`flow` int(10) unsigned NOT NULL,
PRIMARY KEY (`test1_id`),
KEY `IDX_FLOW` (`flow`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `posts_test2`;
CREATE TABLE IF NOT EXISTS `posts_test2` (
`post_id` bigint(20) unsigned NOT NULL,
`test2_id` bigint(20) unsigned NOT NULL,
`type_id` int(10) unsigned NOT NULL DEFAULT 1,
PRIMARY KEY (`post_id`,`test2_id`,`type_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test2`;
CREATE TABLE IF NOT EXISTS `test2` (
`test2_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`power` int(10) unsigned NOT NULL,
PRIMARY KEY (`test2_id`),
KEY `IDX_POWER` (`power`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `types`;
CREATE TABLE IF NOT EXISTS `types` (
`type_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`type` varchar(50) CHARACTER SET ascii DEFAULT NULL,
PRIMARY KEY (`type_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
INSERT INTO `types` (`type_id`, `type`) VALUES
(1, 'a'),
(2, 'b'),
(3, 'c');
INSERT INTO `posts` (`post_id`, `post`) VALUES
(1, 'test1'),
(2, 'test2');
INSERT INTO `test1` (`test1_id`, `flow`) VALUES
(1, 100),
(2, 140),
(3, 200),
(4, 200),
(5, 200);
INSERT INTO `posts_test1` (`post_id`, `test1_id`, `type_id`) VALUES
(1, 1, 1),
(1, 2, 2),
(2, 3, 1),
(2, 4, 2),
(2, 5, 3);
INSERT INTO `test2` (`test2_id`, `power`) VALUES
(1, 1),
(2, 1);
INSERT INTO `posts_test2` (`post_id`, `test2_id`, `type_id`) VALUES
(1, 1, 1),
(1, 2, 2);
這是我的選擇查詢..
SELECT
p.post_id, p.post,
GROUP_CONCAT(t1.flow) flow,
GROUP_CONCAT(t1t.type) flow_types
FROM posts p
LEFT JOIN posts_test1 pt1 USING (post_id)
LEFT JOIN test1 t1 USING (test1_id)
LEFT JOIN types t1t ON (t1t.type_id = pt1.type_id)
GROUP BY p.post_id; # works fine
SELECT
p.post_id, p.post,
GROUP_CONCAT(t2.power) powers,
GROUP_CONCAT(t2t.type) power_types
FROM posts p
LEFT JOIN posts_test2 pt2 USING (post_id)
LEFT JOIN test2 t2 USING (test2_id)
LEFT JOIN types t2t ON (t2t.type_id = pt2.type_id)
GROUP BY p.post_id; # works fine
SELECT
p.post_id, p.post,
GROUP_CONCAT(t1.flow) flow,
GROUP_CONCAT(t1t.type) flow_types,
GROUP_CONCAT(t2.power) powers,
GROUP_CONCAT(t2t.type) power_types
FROM posts p
LEFT JOIN posts_test1 pt1 USING (post_id)
LEFT JOIN test1 t1 USING (test1_id)
LEFT JOIN types t1t ON (t1t.type_id = pt1.type_id)
LEFT JOIN posts_test2 pt2 USING (post_id)
LEFT JOIN test2 t2 USING (test2_id)
LEFT JOIN types t2t ON (t2t.type_id = pt2.type_id)
GROUP BY p.post_id; # getting duplicated GROUP_CONCAT results
SELECT
p.post_id, p.post,
GROUP_CONCAT(DISTINCT t1.flow) flow,
GROUP_CONCAT(DISTINCT t1t.type) flow_types,
GROUP_CONCAT(DISTINCT t2.power) powers,
GROUP_CONCAT(DISTINCT t2t.type) power_types
FROM posts p
LEFT JOIN posts_test1 pt1 USING (post_id)
LEFT JOIN test1 t1 USING (test1_id)
LEFT JOIN types t1t ON (t1t.type_id = pt1.type_id)
LEFT JOIN posts_test2 pt2 USING (post_id)
LEFT JOIN test2 t2 USING (test2_id)
LEFT JOIN types t2t ON (t2t.type_id = pt2.type_id)
GROUP BY p.post_id; # DISTINCT wipes the GROUP_CONCAT if same result...
感謝,並有一個愉快的一天!!
編輯:添加預期結果作為建議,謝謝:)
這里的問題是有兩個不同的連接表(和兩個不同的連接鏈),源自一個表格post
。 所以線性JOIN
鏈不起作用。 當完成線性連接時,其中一個連接表中的重復導致其他鏈中的重復。
一種方法是在兩個單獨的派生表 ( FROM
子句中的子查詢)中考慮這兩個不同的JOIN
鏈,並確定它們各自的分組/聚合表達式。 然后我們可以使用post_id
JOIN
這兩個鏈。
詢問
SELECT
dt1.post_id,
dt1.flows,
dt1.flow_types,
dt2.powers,
dt2.power_types
FROM
(
SELECT
p.post_id,
GROUP_CONCAT(t1.flow) AS flows,
GROUP_CONCAT(typ.type) AS flow_types
FROM posts p
LEFT JOIN posts_test1 pt1
ON pt1.post_id = p.post_id
LEFT JOIN test1 t1
ON t1.test1_id = pt1.test1_id
LEFT JOIN types typ
ON typ.type_id = pt1.type_id
GROUP BY p.post_id
) AS dt1
JOIN
(
SELECT
p.post_id,
GROUP_CONCAT(t2.power) AS powers,
GROUP_CONCAT(typ.type) AS power_types
FROM posts p
LEFT JOIN posts_test2 pt2
ON pt2.post_id = p.post_id
LEFT JOIN test2 t2
ON t2.test2_id = pt2.test2_id
LEFT JOIN types typ
ON typ.type_id = pt2.type_id
GROUP BY p.post_id
) AS dt2
ON dt1.post_id = dt2.post_id;
結果
| post_id | flows | flow_types | powers | power_types |
| ------- | ----------- | ---------- | ------ | ----------- |
| 1 | 100,140 | a,b | 1,1 | a,b |
| 2 | 200,200,200 | a,b,c | | |
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