Question

我正在尝试在以下情况下编写查询

结果

示例：

ColumnA    ColumnB    
A           B         
B           C

结果：

ColumnA   countB   countC
A         1         0
B         0         1

Answer 1

它应该起作用：

  Select 
       columnA,
       count(ColumnB) as ColumnB,
       count(ColumnC) as ColumnC
    From Table
    Group By
       columnA

Answer 2

没有足够的样本数据来确认这一点，但是根据您的问题的标题，您似乎正在寻找条件汇总：

SELECT
    columnA,
    COUNT(CASE WHEN columnB = 'B' THEN 1 END) countB,
    COUNT(CASE WHEN columnB = 'C' THEN 1 END) countC
FROM mytable
GROUP BY columnA

Answer 3

从您的示例数据中，不需要汇总：

SELECT columnA,
       (CASE WHEN columnB = 'B' THEN 1 ELSE 0 END) as countB,
       (CASE WHEN columnB = 'C' THEN 1 ELSE 0 END) as countC
FROM t;

Answer 4

假设您的实际情况比那大，我认为使用枢轴会更好

DECLARE @table TABLE(ColumnA CHAR(1), ColumnB CHAR(1))

INSERT @table VALUES ('A', 'B')
INSERT @table VALUES ('B', 'C')

SELECT ColumnA, A AS CountA, B AS CountB, C AS CountC, D AS CountD....
FROM
(
    SELECT ColumnA, ColumnB
    FROM @table
) AS Source
PIVOT
(
    Count(ColumnB)
    FOR ColumnB IN ([A], [B], [C], [D].....)
) AS Pvt

按一列分组并从多列计数

4 个答案: