Question

我有4列的下表：

id,familyId,memberType,memberName
=================================
1,     1,     main,      RBV
2,     1,     spouse,    VBD
3,     1,     child,     CDE
4,     2,     spouse,    OLL
5,     2,     sibling,   HAQ
6,     3,     main,      OOM
7,     3,     sibling,   NBB
8,     3,     child,     SSS

使用这些数据，我如何编写一个查询来获取每个家庭成员的数量以及该家庭是否有主？

这就是我需要的：

familyId,count,hasMain
=====================
1,     3,     1
2,     2,     0
3,     3,     1

我知道group by familyId会给我每个家庭成员的数量。但它并没有给我这个家庭是否有主要内容。也许这不能在单个查询中实现。

Answer 1

您需要使用汇总函数COUNT()来计算基于familyID和MAX()和CASE语句的所有行，以检查membertype列是否包含主：

SELECT  familyID,
        COUNT(*) AS "Count",
        MAX(CASE WHEN memberType = 'main' THEN 1 ELSE 0 END) AS hasMain
FROM    TableName
GROUP   BY familyID

Answer 2

使用条件聚合和GROUP BY：

SELECT
    familyId,
    COUNT(*) AS family_cnt,
    CASE WHEN SUM(CASE WHEN memberType = 'main' THEN 1 ELSE 0 END) > 0
         THEN 1 ELSE 0 END AS hasMain
FROM
    yourTable
GROUP BY
    familyId;

Answer 3

这是一种方法：

SQL> with test (id, familyid, membertype) as
  2    (select 1, 1, 'main'    from dual union
  3     select 2, 1, 'spouse'  from dual union
  4     select 3, 1, 'child'   from dual union
  5     select 4, 2, 'spouse'  from dual union
  6     select 5, 2, 'sibling' from dual union
  7     select 6, 3, 'main'    from dual union
  8     select 7, 3, 'sibling' from dual union
  9     select 8, 3, 'child'   from dual
 10    ),
 11  hm as
 12    (select familyid
 13     from test
 14     where membertype = 'main'
 15    )
 16  select t.familyid,
 17         count(*) cnt,
 18         decode(hm.familyid, null, 0, 1) hasmain
 19  from test t
 20  left join hm on hm.familyid = t.familyid
 21  group by t.familyid, decode(hm.familyid, null, 0, 1)
 22  order by t.familyid;

  FAMILYID        CNT    HASMAIN
---------- ---------- ----------
         1          3          1
         2          2          0
         3          3          1

SQL>

Answer 4

你也可以试试这个，

SELECT familyid, count(1) count_, MAX(DECODE(membertype, 'main', 1, 0)) has_main
  FROM test
 GROUP BY familyid;

根据某些列值获取行数和标志

4 个答案: