请在SQL帮助上进行数据完整性检查

Question

我有一个问题：

Select distinct yearend, customerid from table1

返回行数为3（SSMS右下角）：

Yearend      CustomerID
2011-03-31   3
2013-10-31   5
2013-12-31   6

我需要做的是得到上面的计数，只返回3的值。

我已尝试过多种变体，但不能只返回＆＃39; 3＆＃39;作为计算总数。

Answer 1

您只需COUNT查询结果：

SELECT COUNT(*)
FROM (
    SELECT DISTINCT yearend, customerid
    FROM table1
)

Answer 2

SELECT count(DISTINCT CustomerID)
FROM table1
GROUP BY CustomerID

Answer 3

你需要特别统计吗？

SELECT COUNT(*)
FROM (
SELECT DISTINCT yearend, customerid
FROM table1
)

Answer 4

select count(*) from
(select distinct yearend, customerid from table1);