mysql - 需要帮助根据 SQL Query 中的特定行信息从多列中获取数据

Question

您好我需要帮助从基于特定行信息（蓝色和红色）的多列中获取数据，然后为每个行条件返回不同的列。

例子 ：

来自 Table_Colours

ID |  Code Type  | Code
1  |  Blue       | Blue1XX
2  |  Red        | Red1XX
2  |  Blue       | Blue1XX
3  |  Red        | Red1XX
4  |  Blue       | Blue1XX
4  |  Red        | Red1XX
5  |  Blue       | Blue1XX

我需要返回

ID | Blue     | Red   
1  | Blue1XX  |        
2  | Blue1XX  | Red1XX
3  |          | Red1XX
4  | Blue1XX  | Red1XX
5  | Blue1XX  |      

蓝色总是返回 Blue1XX（6 个数字代码） 红色总是返回 Red1XX（5 个数字代码）

我需要使用特定的 ID 字符串进行搜索，例如：

AND ID IN (
'1',
'2',
'3',
'4',
)

任何帮助，将不胜感激。

Answer 1

这假定您只有一个或没有与 ID 和特定 CodeType 匹配的内容。此外，它假设 MySQL。如果使用 SQL SERVER，删除LIMIT 1并放在TOP 1每个之后SELECT

SELECT DISTINCT ID, 
       (SELECT Code FROM MyTable AS T1 
        WHERE T1.ID=T0.ID AND T1.`Code Type`='Blue' LIMIT 1) AS BlueCode,
       (SELECT Code FROM MyTable AS T2 
        WHERE T2.ID=T0.ID AND T2.`Code Type`='Red' LIMIT 1) AS RedCode
FROM MyTable T0
WHERE T0.ID IN ('1','2','3')
ORDER BY T0.ID

Answer 2

WITH pair AS (
        WITH red AS (
                SELECT id,  zcode FROM table_colours WHERE code_type = 'Red'
                )
        , blue AS (
                SELECT id,  zcode FROM table_colours WHERE code_type = 'Blue'
                )
        SELECT COALESCE(b.id, r.id) AS id
                , b.zcode AS blue
                , r.zcode AS red
        FROM blue b
        FULL JOIN red r ON r.id = b.id
        )
SELECT * FROM pair
WHERE id IN (1,2,3,4)
        ;

结果：

 id |  blue   |  red   
----+---------+--------
  1 | Blue1XX | 
  2 | Blue1XX | Red1XX
  4 | Blue1XX | Red1XX
  3 |         | Red1XX
(4 rows)

注意：mysql-tag 是后来添加的。（mysql 不允许 CTE 的）

对 OP：你应该早先说过“它是 mysql”。在这种情况下，我不会费心创建基于 CTE 的答案。

Answer 3

尝试这个：

select id, code as 'Blue', null as 'Red'
from table
where code_type like 'Blue'

union

select id, null as 'Blue', code as 'Red'
from table
where code_type like 'Red'