sqlite中的分组行未按预期工作
因此,我想对所有标题相同的文章进行分组:sqlite中的分组行未按预期工作,sql,sqlite,Sql,Sqlite,因此,我想对所有标题相同的文章进行分组: CREATE TABLE Article( ID INTEGER NOT NULL, Title TEXT ); CREATE TABLE Tag( ID INTEGER NOT NULL, Name TEXT ); CREATE TABLE Article_Tag( Article_ID INTEGER NOT NULL, Tag_ID INTEGER NOT NULL, PRIMARY KEY
CREATE TABLE Article(
ID INTEGER NOT NULL,
Title TEXT
);
CREATE TABLE Tag(
ID INTEGER NOT NULL,
Name TEXT
);
CREATE TABLE Article_Tag(
Article_ID INTEGER NOT NULL,
Tag_ID INTEGER NOT NULL,
PRIMARY KEY (Article_ID,Tag_ID)
);
INSERT INTO Article (ID, Title) VALUES
(1, 'wifi'),
(2, 'bluetooth'),
(3, 'firewire');
INSERT INTO Tag (ID, Name) VALUES
(1, 'tag 1'),
(2, 'tag 2'),
(3, 'tag 3');
INSERT INTO Article_Tag (Article_ID, Tag_ID) VALUES
(1, 1),
(1, 2),
(1, 3),
(2, 1);
--------------------------------------
SELECT
a.Title,
t.Name AS TagName
FROM Article AS a
LEFT OUTER JOIN Article_Tag AS a_t ON a.ID = a_t.Article_ID
LEFT OUTER JOIN Tag t ON t.ID = a_t.Tag_ID
--------------------------------------
Title TagName
wifi tag 1
wifi tag 2
wifi tag 3
bluetooth tag 1
firewire (null)
但我想要这个:
SELECT
a.Title,
GROUP_CONCAT(t.Name,';') AS TagNames
FROM Article AS a
LEFT OUTER JOIN Article_Tag AS a_t ON a.ID = a_t.Article_ID
LEFT OUTER JOIN Tag t ON t.ID = a_t.Tag_ID
--------------------------------------
Title TagNames
firewire tag 1;tag 2;tag 3;tag 1
我做错了什么?只需添加一个
GROUPBY
子句
Title TagNames
wifi tag 1; tag 2; tag3
bluetooth tag 1;
firewire (null)
若要以相同的顺序获得相同的结果,请添加“a.id分组”广告,如下所示:
SELECT
a.Title,
GROUP_CONCAT(t.Name,';') AS TagNames
FROM Article AS a
LEFT OUTER JOIN Article_Tag AS a_t ON a.ID = a_t.Article_ID
LEFT OUTER JOIN Tag t ON t.ID = a_t.Tag_ID
group by a.title
此处演示:
因为你应该根据问题
得到每个标题一行,我想对所有标题相同的文章进行分组
啊,我明白了,没有这一点,sqlite就不知道如何对group\u concat
请求的t.Name
列进行分组。很有道理。
SELECT
a.Title,
GROUP_CONCAT(t.Name,';') AS TagNames
FROM Article AS a
LEFT OUTER JOIN Article_Tag AS a_t ON a.ID = a_t.Article_ID
LEFT OUTER JOIN Tag t ON t.ID = a_t.Tag_ID
group by a.id