将查询结果存储到变量中并在存储过程中对其进行修改

Question

我有一个网站,客户在网上订购东西,在购物车模型等.

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一次到达数据库根据需要修改结果,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,我认为通过SQL Server进行操作Stored Procedures将是一个更好的主意.但即使经过尝试和发现很多,我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,请如何指导.

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

用于调用存储过程的SQL命令

EXEC MyProc