在 SQL 中将列转换为行 [英] Convert columns to rows in SQL

问题描述

我需要编写一个查询，它接受行并将其转换为列 - 这是我的表:

I need to write a query which takes rows and converts it into columns - here's my table:

Count    fname   lname   id
-----------------------------
1        abc     def    20
2        pqr            20      
3        abc     xyz    20  
4        xyz     xyz    20
1        abc     def    21
1        pqr     xyz    22
2        abc     abc    22

这是我试图产生的输出:

This is the output I'm trying to produce:

id  fname  lname  fname  lname  fname  lname  fname  lname
-------------------------------------------------------------
20  abc    def    pqr    NULL   abc    xyz    xyz    xyz
21  abc    def    NULL   NULL   NULL   NULL   NULL   NULL   
22  abc    abc    NULL   NULL   NULL   NULL   NULL   NULL

每个 id 的 count 最大值为 4.我使用的是 Oracle 9i.

The max value of count for each id is 4. I'm using Oracle 9i.

推荐答案

这是另一个你可能会遇到的问题.我喜欢@ThinkJet，但不确定解码成本是多少(如果多于或少于以下.

Here's another one you might have some luck with. I like @ThinkJet's but not sure how much decode costs (if more or less than this below.

SELECT
   T1.ID,
   T1.fname,
   T1.lname,
   T2.fname,
   T2.lname,
   T3.fname,
   T3.lname,
   T4.fname,
   T4.lname
FROM
      table T1
   LEFT JOIN
      table T2
   ON
         T1.ID = T2.ID
      AND T2.count = 2
   LEFT JOIN
      table T3
   ON
         T1.ID = T3.ID
      AND T3.count = 3
   LEFT JOIN
      table T4
   ON
         T1.ID = T4.ID
      AND T4.count = 4
WHERE
   T1.count = 1

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