编写一个查询以从sql表中获取所需的内容

问题描述

[]点击链接获取表格和所需的输出。这个问题是由一家公司在技术考试中提出的。我无法回答。请告诉我如何获得解决方案。

http://stackoverflow.com/questions/25033601/write-a-query-to-get-desired-sql-table-output[^] click on the link to get the tables and desired output. This question is asked by a company at technical exam. I could not given answer. Please tell me how can i get the solution.

推荐答案

SELECT
M.EMPID
,CASE WHEN M.ID = 1 THEN TA.NAME
      WHEN M.ID = 2 THEN TB.NAME
      WHEN M.ID = 3 THEN TC.NAME
      WHEN M.ID = 4 THEN TD.NAME
FROM
MASTER M
LEFT JOIN TABLEA  TA ON TA.EMPID = M.EMPID
LEFT JOIN TABLEB  TA ON TB.EMPID = M.EMPID
LEFT JOIN TABLEB  TC ON TC.EMPID = M.EMPID
LEFT JOIN TABLEB  TD ON TD.EMPID = M.EMPID

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