Question

我有一个网站，客户在网上订购东西，购物车模型等。

问题是，当我知道订单被记录时，有不同的信息需要更新，如订单表中的条目，库存表中的扣除，更新销售表等。我目前通过运行每个单个查询来执行此操作数据库根据需求修改结果的时间，然后运行另一个查询来更新结果，因为下一个查询需要来自前一个查询的信息：

        bool stts = false;
        int re1 = 0, re2 = 0, re3 = 0;
        short maxOr = 0, maxCa = 0, maxOc = 0;
        SqlConnection conn= Shared.GetSqlCon(); //Make connection object

        conn= Shared.GetSqlCon();
        var comm1 = new Commmand("SELECT MAX(orId) FROM [order];", sqlCon);
        maxOr = Shared.OSC(sqlCon, comm1);
        Shared.COC(sqlCon); //Close & Dispose connections

        conn= Shared.GetSqlCon();
        var comm2 = new Commmand("SELECT MAX(caId) FROM [cart];", sqlCon);
        maxCa = Shared.OSC(sqlCon, comm2);
        Shared.COC(sqlCon);

        conn= Shared.GetSqlCon();
        var comm3 = new Commmand("INSERT INTO [order_cart](orId,caId) VALUES(@maxOr,@maxCa);", sqlCon);
        comm3.Parameters.AddWithValue("@maxOr", maxOr + 1);
        comm3.Parameters.AddWithValue("@maxCa", maxCa + 1);

当然，这无论如何都不是一次又一次地回到数据库的好方法，而且我认为通过SQL Server Stored Procedures进行操作会更好。但即使经过尝试和发现很多，我也找不到一个如何将查询结果存储在SP变量中并在其中使用它的示例，有点像这样：

Declare @myVar int //Stored Procedure variable
@myVar = SELECT MAX(caId) FROM [cart] //Getting query result in the variable
INSERT INTO [order_cart](orId,caId) VALUES(@maxOr, @myVar); //Updating record through the variable
return @myVar //return variable value to the program

这可能吗？如果是，请指导。

Answer 1

是的，这当然是可能的。以下是几个例子。

-- one way to do this
DECLARE @Cnt int

SELECT @Cnt = COUNT(SomeColumn)
FROM TableName
GROUP BY SomeColumn

-- another way to do the same thing
DECLARE @StreetName nvarchar(100)
SET @StreetName = (SELECT Street_Name from Streets where Street_ID = 123)

-- Assign values to several variables at once
DECLARE @val1 nvarchar(20)
DECLARE @val2 int
DECLARE @val3 datetime
DECLARE @val4 uniqueidentifier
DECLARE @val5 double

SELECT @val1 = TextColumn,
@val2 = IntColumn,
@val3 = DateColumn,
@val4 = GuidColumn,
@val5 = DoubleColumn
FROM SomeTable

Answer 2

试试这个例子

CREATE PROCEDURE MyProc
BEGIN
    --Stored Procedure variables
    Declare @maxOr int; 
    Declare @maxCa int; 

    --Getting query result in the variable (first variant of syntax)
    SET @maxOr = (SELECT MAX(orId) FROM [order]); 

    --Another variant of seting variable from query
    SELECT @maxCa=MAX(caId) FROM [cart]; 

    --Updating record through the variable
    INSERT INTO [order_cart] (orId,caId)
    VALUES(@maxOr, @maxCa); 

    --return values to the program as dataset
    SELECT
       @maxOr AS maxOr,
       @maxCa AS maxCa

    -- return one int value as "return value"
    RETURN @maxOr
END
GO

调用存储过程的SQL命令

EXEC MyProc

Answer 3

或者您可以使用一个SQL命令而不是create和call stored procedure

INSERT INTO [order_cart](orId,caId)
OUTPUT inserted.*
SELECT
   (SELECT MAX(orId) FROM [order]) as orId,
   (SELECT MAX(caId) FROM [cart]) as caId;

将查询结果存储到变量中并在存储过程中对其进行修改

3 个答案: