有一个表：
在4个字段里面都有教师ID，想统计这4个字段里面出现过的教师ID都有哪些，咋办？
结果就像下面表示的，只有一个字段
教师ID
3
4
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首先你的表设计就不合理
非要这么做就 select * from table group by 字段1 +字段2 + 字段3
------解决思路----------------------
你为什么不能设计成老师ID+课程类型Type呢？
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设计不合理。查询还得4组转成1组。
SELECT 教师ID
FROM (
SELECT DISTINCT [1、2节教师ID] AS 教师ID, 1 AS 节 FROM 表1 WHERE [1、2节教师ID] IS NOT NULL
UNION ALL
SELECT DISTINCT [3、4节教师ID] AS 教师ID, 3 AS 节 FROM 表1 WHERE [3、4节教师ID] IS NOT NULL
UNION ALL
SELECT DISTINCT [5、6节教师ID] AS 教师ID, 5 AS 节 FROM 表1 WHERE [5、6节教师ID] IS NOT NULL
UNION ALL
SELECT DISTINCT [7、8节教师ID] AS 教师ID, 7 AS 节 FROM 表1 WHERE [7、8节教师ID] IS NOT NULL
) AS T
GROUP BY 教师ID
HAVING COUNT(节) = 4;