在select语句中对数据进行分组

Question

我有大量数据需要在检索时分类到不同的组.每组都有不同的条件.我不想单独检索它们.我想知道使用单个sql语句的每个组中的项目数.

例如,伪代码将如下所示:

Select count(IssueID) as Issue1_Count if(condition1), 
count(IssueID) as Issue2_Count if(condition2),
count(IssueID) as Issue3_Count if(condition3)
From table1, table2, tabl3
where common_condition1 and common_Condition2;

有人可以帮我制作一个Oralce查询...

Answer 1

这样说:

SELECT 
       SUM(CASE WHEN condition1 THEN 1 ELSE 0 END) as Issue1_Count,
       SUM(CASE WHEN condition2 THEN 1 ELSE 0 END) as Issue2_Count,
       SUM(CASE WHEN condition3 THEN 1 ELSE 0 END) as Issue3_Count,
FROM 
       table1, table2, tabl3
WHERE 
       common_condition1 and common_Condition2;