条件计数在一个字段上
如果我有这样的桌子：
jobId, jobName, Priority 其中Priority可以是1到5之间的整数。
因为我需要这个查询来生成报表上的图表，所以我需要显示jobid，jobname和5个称为Priority1，Priority2，Priority3，Priority4的字段。 Priority5。
Priority1应计算优先级字段值为1的行数。
Priority2应计算优先级字段值为2的行数。
Priority3应计算优先级字段值为3的行数。
等等
我将如何快速和高效地做到这一点？
非常感谢，卡夫
我想你可能会在之后
select jobID, JobName, sum(case when Priority = 1 then 1 else 0 end) as priority1, sum(case when Priority = 2 then 1 else 0 end) as priority2, sum(case when Priority = 3 then 1 else 0 end) as priority3, sum(case when Priority = 4 then 1 else 0 end) as priority4, sum(case when Priority = 5 then 1 else 0 end) as priority5 from Jobs group by jobID, JobName
然而，我不确定你是否需要在结果中的jobID和JobName，如果这样删除它们并删除组，
使用COUNT而不是SUM删除ELSE语句的需求：
SELECT jobId, jobName, COUNT(CASE WHEN Priority=1 THEN 1 END) AS Priority1, COUNT(CASE WHEN Priority=2 THEN 1 END) AS Priority2, COUNT(CASE WHEN Priority=3 THEN 1 END) AS Priority3, COUNT(CASE WHEN Priority=4 THEN 1 END) AS Priority4, COUNT(CASE WHEN Priority=5 THEN 1 END) AS Priority5 FROM TableName GROUP BY jobId, jobName
使用ANSI SQL-92 CASE语句，你可以做这样的事情（派生表加上大小写）：
SELECT jobId, jobName, SUM(Priority1) AS Priority1, SUM(Priority2) AS Priority2, SUM(Priority3) AS Priority3, SUM(Priority4) AS Priority4, SUM(Priority5) AS Priority5 FROM ( SELECT jobId, jobName, CASE WHEN Priority = 1 THEN 1 ELSE 0 END AS Priority1, CASE WHEN Priority = 2 THEN 1 ELSE 0 END AS Priority2, CASE WHEN Priority = 3 THEN 1 ELSE 0 END AS Priority3, CASE WHEN Priority = 4 THEN 1 ELSE 0 END AS Priority4, CASE WHEN Priority = 5 THEN 1 ELSE 0 END AS Priority5 FROM TableName )
IIF不是一个标准的SQL构造，但是如果它受到数据库的支持，则可以获得更优雅的语句，从而产生相同的结果：
SELECT JobId, JobName, COUNT(IIF (Priority=1, 1, NULL)) AS Priority1, COUNT(IIF (Priority=2, 1, NULL)) AS Priority2, COUNT(IIF (Priority=3, 1, NULL)) AS Priority3, COUNT(IIF (Priority=4, 1, NULL)) AS Priority4, COUNT(IIF (Priority=5, 1, NULL)) AS Priority5 FROM TableName GROUP BY JobId, JobName
SELECT Priority, COALESCE(cnt, 0) FROM ( SELECT 1 AS Priority UNION ALL SELECT 2 AS Priority UNION ALL SELECT 3 AS Priority UNION ALL SELECT 4 AS Priority UNION ALL SELECT 5 AS Priority ) p LEFT JOIN ( SELECT Priority, COUNT(*) AS cnt FROM jobs GROUP BY Priority ) j ON j.Priority = p.Priority
你可以join表格：
select t.jobId, t.jobName, count(p1.jobId) as Priority1, count(p2.jobId) as Priority2, count(p3.jobId) as Priority3, count(p4.jobId) as Priority4, count(p5.jobId) as Priority5 from theTable t left join theTable p1 on p1.jobId = t.jobId and p1.jobName = t.jobName and p1.Priority = 1 left join theTable p2 on p2.jobId = t.jobId and p2.jobName = t.jobName and p2.Priority = 2 left join theTable p3 on p3.jobId = t.jobId and p3.jobName = t.jobName and p3.Priority = 3 left join theTable p4 on p4.jobId = t.jobId and p4.jobName = t.jobName and p4.Priority = 4 left join theTable p5 on p5.jobId = t.jobId and p5.jobName = t.jobName and p5.Priority = 5 group by t.jobId, t.jobName
或者你可以使用一个总和内的情况：
select jobId, jobName, sum(case Priority when 1 then 1 else 0 end) as Priority1, sum(case Priority when 2 then 1 else 0 end) as Priority2, sum(case Priority when 3 then 1 else 0 end) as Priority3, sum(case Priority when 4 then 1 else 0 end) as Priority4, sum(case Priority when 5 then 1 else 0 end) as Priority5 from theTable group by jobId, jobName
我需要显示jobid，jobname和称为Priority1，Priority2，Priority3，Priority4的5个字段。 Priority5。
你的查询devise有问题。 你也在每一行显示一个特定的工作，所以你要么有一个行有四个优先级列'0'和一个优先级列'1'（该作业的优先级）否则你将最终重复每一行所有优先级的计数。
你真的想在这里展示什么？
SELECT Count（Student_ID）as'StudentCount'FROM CourseSemOne where Student_ID = 3计数（Student_ID）<6且计数（Student_ID）> 0;
