sql-server - 如何在mssql中计算具有特定数据的行数

Question

我有下表:

项目:

ID     Type     StockExists  
01     Cellphone   T
02     Cellphone   F
03     Apparrel    T

我要 count the number of items与现有股票，即行数 StockExists='T' .我正在执行查询；

Select count(StockExists) 
From [Items] where StockExists='T'

但它总是返回 1. 正确的做法是什么？

编辑:

另外，如何执行另一个这样的 Count 操作并将它们添加到一行中，例如，

Select count(StockExists) 
From [Items] where StockExists='T'` and `Select count(Type) 
From [Items] where Type='Cellphone'` ? 

Answer 1

SELECT 
    COUNT(*) As ExistCount 
FROM 
    dbo.Items
WHERE
    StockExists='T'

所以你的查询应该有效。

结果:

EXISTCOUNT
    2

Demo

更新

How to perform another such Count operation and add them together in one row, for example, Select count(StockExists) From [Items] where StockExists='T' and Select count(Type) From [Items] where Type='Cellphone' ?

您可以使用 SUM与 CASE :

SELECT 
  ExistCount = SUM(CASE WHEN StockExists='T' THEN 1 ELSE 0 END) ,
  CellphoneCount = SUM(CASE WHEN Type='Cellphone' THEN 1 ELSE 0 END) 
FROM 
    dbo.Items

结果:

EXISTCOUNT    CELLPHONECOUNT
    2               2

Demo