我想檢索一個字段中的每個計數特定數據

Question

有沒有辦法做到這一點？我想檢索數據的每個計數在一個領域

這裏是我的代碼..

Dim cmd1 As New SqlCommand("SELECT COUNT(support) AS support " & _ 
          "FROM Studz_Table WHERE support ='others'",conn) 
dim int1 as integer = cmd1.executescalar 

Dim cmd2 As New SqlCommand("SELECT COUNT(support) AS support " & _ 
          "FROM Studz_Table WHERE support ='myself'",conn) 
dim int2 as integer = cmd1.executescalar 
Dim cmd3 As New SqlCommand("SELECT COUNT(support) AS support " & _ 
          "FROM Studz_Table WHERE support ='parent'",conn) 
dim int3 as integer = cmd1.executescalar 

有沒有簡單的方法來做到這一點？

Answer 1

您可以使用SUM和CASE的組合來檢索每種類型的計數。

Dim cmd As New SqlCommand("SELECT SUM(CASE WHEN support = 'others' THEN 1 ELSE 0 END) AS OthersCount, " & _ 
          "SUM(CASE WHEN support = 'myself' THEN 1 ELSE 0 END) AS MyselfCount, " & _ 
          "SUM(CASE WHEN support = 'parent' THEN 1 ELSE 0 END) AS ParentCount " & _ 
          "FROM Studz_Table WHERE support ='others'",conn) 

你需要使用ExecuteReader雖然不是ExecuteScalar訪問每一列：

SqlDataReader reader = command.ExecuteReader(); 
while (reader.Read()) 
{ 
    int int1 = reader[0]; 
    int int2 = reader[1]; 
    int int3 = reader[2]; 
}