Question

我想在SQL Compact 4.0 DB-Table上进行查询，其中包含2个COUNT（） - 列。第一列应计算所有行（COUNT（*）），第二列仅计算行，当特定列的十进制值高于或等于3.0时

我到目前为止：

SELECT COUNT(a.number) AS Participant, COUNT(b.specificColumn) AS Approved
FROM person AS a 
LEFT OUTER JOIN test AS b 
ON b.number = a.number

这样第二个COUNT（）显然只计算实际有值的行！= NULL

Answer 1

我认为你不能用计数做到这一点。尝试使用案例陈述。未经测试：

SELECT COUNT(a.number) AS Participant, 
SUM(case when b.specificColumn >3 then 1 else 0 end) as Approved
FROM person AS a 
LEFT OUTER JOIN test AS b 
ON b.number = a.number

Answer 2

SELECT COUNT(a.number) AS Participant,
       SUM(CASE WHEN b.specificColumn IS NULL THEN 0
                WHEN b.specificColumn >= 3 THEN 1
                ELSE 0) AS Approved
FROM person AS a 
LEFT OUTER JOIN test AS b 
ON b.number = a.number

COUNT（）列按特定值

2 个答案: