Question

对于如下表格：

foo_table

id | str_col | bool_col

 1   "1234"     0
 2   "3215"     0
 3   "8132"     1
 4   NULL       1
 5   ""         1
 6   ""         0

我知道如何查询：

count(*) | bool_col
   3          0
   3          1

和

count(*) | isnull(str_col) or str_col = ""
   3          0
   3          1

但我怎么能得到类似的东西：

count(*) | bool_col | isnull(str_col) or str_col = ""
   2          0           0
   1          0           1
   1          1           0
   2          1           1

与此同时，我只是单独做：

select count(*) from foo_table where bool_col and (isnull(str_col) or str_col = "");
select count(*) from foo_table where not bool_col and (isnull(str_col) or str_col = "");
select count(*) from foo_table where bool_col and not (isnull(str_col) or str_col = "");
select count(*) from foo_table where not bool_col and not (isnull(str_col) or str_col = "");

Answer 1

尝试

SELECT COUNT(*), 
       bool_col, 
       CASE WHEN str_col IS NULL OR str_col = '' THEN 1 ELSE 0 END str_col
  FROM foo_table
 GROUP BY bool_col, 
       CASE WHEN str_col IS NULL OR str_col = '' THEN 1 ELSE 0 END

输出（MySql）：

| COUNT(*) | BOOL_COL | STR_COL |
---------------------------------
|        2 |        0 |       0 |
|        1 |        0 |       1 |
|        1 |        1 |       0 |
|        2 |        1 |       1 |

SQLFiddle MySQL

SQLFiddle SQL Server

Answer 2

SELECT COUNT(CASE 
 WHEN bool_col AND (isnull(str_col) or str_col = "")  THEN 1 
END) as c1,
COUNT(CASE 
 WHEN not bool_col and (isnull(str_col) or str_col = "") THEN 1
END) as c2,
COUNT(CASE 
 WHEN bool_col and not (isnull(str_col) or str_col = "") THEN 1
END) as c3,
COUNT(CASE 
 WHEN not bool_col and not (isnull(str_col) or str_col = "") THEN 1
END) as c4
FROM table1

Answer 3

在oracle中有一个名为cube

的内置函数

select  bool_col , 
        case when str_col is null or str_col = '' then 1 else 0 end str_col ,
        count(*)
from    table1
group by cube (bool_col , case when str_col is null or str_col = '' then 1 else 0 end)

cube将为您提供所有组合。还有rollup这是cube的私人案例。

如何按多列组合计数和分组？

3 个答案: