SQL 将行转换为列

Question

我有以下输出：

Username	shortname	data
test1	firm	Google
test1	type	IT
test1	agreed	1
test2	firm	Facebook
test2	type	IT
test2	agreed	1
test2	newsletter	1

我想创建另一个专栏，内容如下：如果用户名的简称为“newsletter”，并且“newsletter”的数据为“1”，则为“yes”，如果用户名没有 newsletter，则为“no”。 =14=]

所以我想得到以下输出：

Username	yes/no
test1	no
test2	yes

我做了以下代码：

SELECT distinct(if(shortname = 'newsletter' and data = 1, 'Yes', 'No')) as 'Yes/no', username
FROM prefix_user as u
JOIN prefix_user_info_data as uid ON uid.userid = u.id
JOIN prefix_user_info_field as uif ON uid.fieldid = uif.id

但这会在每一行中写出是或否

Answer 1

这是在 Oracle 上吗？实际上，即使不是，您也可以在下面的查询中采纳这个想法。

select case 
        when shortname = 'newsletter' and data = '1'
         then 'YES' 
        else 'NO' 
       end as yes_no 
  from prefix_user as u 
  JOIN prefix_user_info_data as uid 
    ON uid.userid = u.id 
  JOIN prefix_user_info_field as uif 
    ON uid.fieldid = uif.id

Answer 2

根据您添加的标签，我将其视为 MySQL。在你的 IF 条件中，在 shortname='newsletter' 的情况下，你将不得不添加一个嵌套的 IF 条件来检查数据值是否等于 1.

查询将类似于以下内容，用于检查将根据 IF 条件选择所有用户而不是 DISTINCT：

SELECT
    IF( shortname = 'newsletter',
        IF (
            data= 1,
            'yes',
        'No')
    , 'No') AS 'Yes/no',
    username,shortname, data
FROM
    test1 AS u   //Relace your table name here
//add joins with other tables that you requires.

Answer 3

您可以使用条件聚合作为

SELECT username,
       MAX(CASE
           WHEN shortname = 'newsletter' AND data = 1 THEN
            'Yes'
           ELSE
            'No'
           END) AS "yes/no"
  FROM prefix_user as u
  JOIN prefix_user_info_data as uid
    ON uid.userid = u.id
  JOIN prefix_user_info_field as uif
    ON uid.fieldid = uif.id
 GROUP BY username

考虑到单词的字母顺序 Yes 晚于 No

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