OUTPUT是SQL SERVER2005的新特性,可以从数据修改语句中返回输出,可以看作是"返回结果的DML"。
INSERT、DELETE、UPDATE均支持OUTPUT子句。
在OUTPUT子句中,可以引用特殊表inserted和deleted,使用inserted和deleted表与在触发器中使用的非常相似。
对于包含自增列的表执行多行insert语句,同时想知道新的标识值时,在INSERT中使用OUTPUT子句非常方便。
1、对于单行INSERT语句,这不成问题:SCOPE_IDENTITY函数即可实现。SCOPE_IDENTITY函数:返回为当前会话和当前作用域中的任何表最后生成的标识值。
-- Generating Surrogate Keys for Customers USE tempdb; GO IF OBJECT_ID('dbo.CustomersDim') IS NOT NULL DROP TABLE dbo.CustomersDim; GO CREATE TABLE dbo.CustomersDim ( KeyCol INT NOT NULL IDENTITY PRIMARY KEY, CustomerID NCHAR(5) NOT NULL, CompanyName NVARCHAR(40) NOT NULL, ); -- Insert New Customers and Get their Surrogate Keys DECLARE @NewCusts TABLE ( CustomerID NCHAR(5) NOT NULL PRIMARY KEY, KeyCol INT NOT NULL UNIQUE ); INSERT INTO dbo.CustomersDim(CustomerID, CompanyName) OUTPUT inserted.CustomerID, inserted.KeyCol INTO @NewCusts -- OUTPUT inserted.CustomerID, inserted.KeyCol SELECT CustomerID, CompanyName FROM Northwind.dbo.Customers WHERE Country = N'UK'; SELECT CustomerID, KeyCol FROM @NewCusts; GO
注意代码中被注释掉的第二个OUTPUT子句,后面没有INTO子句。如果还要输出返回给调用方,取消注释即可。这样INSERT语句将包含两个OUTPUT子句。
2、多行INSERT语句
USE AdventureWorks; GO CREATE TABLE TestTable (ID INT, TEXTVal VARCHAR(100)) DECLARE @TmpTable TABLE (ID INT, TEXTVal VARCHAR(100)) INSERT TestTable (ID, TEXTVal) OUTPUT Inserted.ID, Inserted.TEXTVal INTO @TmpTable VALUES (1,'FirstVal') INSERT TestTable (ID, TEXTVal) OUTPUT Inserted.ID, Inserted.TEXTVal INTO @TmpTable VALUES (2,'SecondVal') SELECT * FROM @TmpTable SELECT * FROM TestTable DROP TABLE TestTable GO
如果要删除数据的同时,还需要记录日志,或者归档数据,在DELETE中使用OUTPUT子句在适合不过了。
USE AdventureWorks; GO CREATE TABLE TestTable (ID INT, TEXTVal VARCHAR(100)) DECLARE @TmpTable TABLE (ID INT, TEXTVal VARCHAR(100)) INSERT TestTable (ID, TEXTVal) VALUES (1,'FirstVal') INSERT TestTable (ID, TEXTVal) VALUES (2,'SecondVal') DELETE FROM TestTable OUTPUT Deleted.ID, Deleted.TEXTVal INTO @TmpTable WHERE ID IN (1,2) SELECT * FROM @TmpTable SELECT * FROM TestTable DROP TABLE TestTable GO
USE AdventureWorks; GO CREATE TABLE TestTable (ID INT, TEXTVal VARCHAR(100)) DECLARE @TmpTable TABLE (ID_New INT, TEXTVal_New VARCHAR(100),ID_Old INT, TEXTVal_Old VARCHAR(100)) INSERT TestTable (ID, TEXTVal) VALUES (1,'FirstVal') INSERT TestTable (ID, TEXTVal) VALUES (2,'SecondVal') UPDATE TestTable SET TEXTVal = 'NewValue' OUTPUT Inserted.ID, Inserted.TEXTVal, Deleted.ID, Deleted.TEXTVal INTO @TmpTable WHERE ID IN (1,2) SELECT * FROM @TmpTable SELECT * FROM TestTable DROP TABLE TestTable GO
以下示例使用指定的 ProductID
和 ScrapReasonID
,针对 WorkOrder
表中的所有工作顺序更新 ScrapReasonID
列。
OUTPUT INTO
子句返回所更新表 (WorkOrder
) 中的值以及 Product
表中的值。 在 Product
子句中使用 FROM
表来指定要更新的行。
由于 WorkOrder
表上定义了 AFTER UPDATE
触发器,因此需要 INTO
关键字。
USE AdventureWorks2012; GO DECLARE @MyTestVar TABLE ( OldScrapReasonID INT NOT NULL, NewScrapReasonID INT NOT NULL, WorkOrderID INT NOT NULL, ProductID INT NOT NULL, ProductName NVARCHAR(50)NOT NULL); UPDATE Production.WorkOrder SET ScrapReasonID = 4 OUTPUT deleted.ScrapReasonID, inserted.ScrapReasonID, inserted.WorkOrderID, inserted.ProductID, p.Name INTO @MyTestVar FROM Production.WorkOrder AS wo INNER JOIN Production.Product AS p ON wo.ProductID = p.ProductID AND wo.ScrapReasonID= 16 AND p.ProductID = 733; SELECT OldScrapReasonID, NewScrapReasonID, WorkOrderID, ProductID, ProductName FROM @MyTestVar; GO
下面的示例捕获从 OUTPUT
语句的 MERGE
子句返回的数据,并将这些数据插入另一个表。
MERGE
语句每天根据在 Quantity
表中处理的订单更新 ProductInventory
表的 SalesOrderDetail
列。 如果产品的库存降至 0
或更低,它还会删除与这些产品对应的行。
本示例捕获已删除的行并将这些行插入另一个表 ZeroInventory
中,该表跟踪没有库存的产品。
USE AdventureWorks2012; GO IF OBJECT_ID(N'Production.ZeroInventory', N'U') IS NOT NULL DROP TABLE Production.ZeroInventory; GO --Create ZeroInventory table. CREATE TABLE Production.ZeroInventory (DeletedProductID int, RemovedOnDate DateTime); GO INSERT INTO Production.ZeroInventory (DeletedProductID, RemovedOnDate) SELECT ProductID, GETDATE() FROM ( MERGE Production.ProductInventory AS pi USING (SELECT ProductID, SUM(OrderQty) FROM Sales.SalesOrderDetail AS sod JOIN Sales.SalesOrderHeader AS soh ON sod.SalesOrderID = soh.SalesOrderID AND soh.OrderDate = '20070401' GROUP BY ProductID) AS src (ProductID, OrderQty) ON (pi.ProductID = src.ProductID) WHEN MATCHED AND pi.Quantity - src.OrderQty <= 0 THEN DELETE WHEN MATCHED THEN UPDATE SET pi.Quantity = pi.Quantity - src.OrderQty OUTPUT $action, deleted.ProductID) AS Changes (Action, ProductID) WHERE Action = 'DELETE'; IF @@ROWCOUNT = 0 PRINT 'Warning: No rows were inserted'; GO SELECT DeletedProductID, RemovedOnDate FROM Production.ZeroInventory;
以下语句中不支持 OUTPUT 子句:
返回单列:
using(SqlCommand cmd=new SqlCommand("INSERT INTO Mem_Basic(Mem_Na,Mem_Occ) output INSERTED.ID VALUES(@na,@occ)",con)) { cmd.Parameters.AddWithValue("@na", Mem_NA); cmd.Parameters.AddWithValue("@occ", Mem_Occ); con.Open(); int modified =(int)cmd.ExecuteScalar(); if (con.State == System.Data.ConnectionState.Open) con.Close(); return modified; }
返回多行或者多列:
create table Suspension (pkey int not null identity(1, 1), pallet_position int, processing_pallet_pkey int, datetime_created datetime, datetime_updated datetime, [this.created_by] int, [this.updated_by] int); using (var conn = new SqlConnection(connectionString)) { conn.Open(); const string insertQuery = @" INSERT INTO dbo.Suspension (pallet_position, processing_pallet_pkey, datetime_created, datetime_updated, [this.created_by], [this.updated_by]) OUTPUT INSERTED.pkey VALUES (1, 2, '20141013 16:27:25.000', '20141013 16:27:25.000', 2, 2), (2, 2, '20141013 16:27:25.000', '20141013 16:27:25.000', 2, 2), (3, 2, '20141013 16:27:25.000', '20141013 16:27:25.000', 2, 2), (4, 2, '20141013 16:27:25.000', '20141013 16:27:25.000', 2, 2);"; // 通过数据库 DataTable dt = new DataTable(); using (SqlCommand cmd = new SqlCommand(insertQuery, conn)) using (var insertedOutput = cmd.ExecuteReader()) { dt.Load(insertedOutput); } Console.WriteLine(dt.Rows.Count); // 4 // 通过手工读取 var list = new List<int>(); using (SqlCommand cmd = new SqlCommand(insertQuery, conn)) using (var insertedOutput = cmd.ExecuteReader()) { while(insertedOutput.Read()) { list.Add(insertedOutput.GetInt32(0)); } } Console.WriteLine(list.Count); // 4 // 通过dapper var ids = conn.Query<int>(insertQuery).ToList(); Console.WriteLine(ids.Count); // 4 }