我该如何更新SQL表逻辑

我有一个结构为，

Table 3 Fruit ID - Foreign Key (Primary Key of Table 1) Crate ID - Foreign Key (Primary Key of Table 2) 

现在我需要执行一个查询，

如果 Fruit ID 已经在Table中，则 更新 Fruit ID Crate ID ，如果没有，则将表3中的记录作为新记录插入。

这就是我现在在代码中得到的，

 private void RelateFuirtWithCrates(List selectedFruitIDs, int selectedCrateID) { string insertStatement = "INSERT INTO Fruit_Crate(FruitID, CrateID) Values " + "(@FruitID, @CrateID);"; ?? I don't think if it's right query using (SqlConnection connection = new SqlConnection(ConnectionString())) using (SqlCommand cmd = new SqlCommand(insertStatement, connection)) { connection.Open(); cmd.Parameters.Add(new SqlParameter("@FruitID", ????? Not sure what goes in here)); cmd.Parameters.Add(new SqlParameter("@CrateID",selectedCrateID)); } 

Answer 1

您可以在SQL Server中使用MERGE语法执行“upsert”：

 MERGE [SomeTable] AS target USING (SELECT @FruitID, @CrateID) AS source (FruitID, CrateID) ON (target.FruitID = source.FruitID) WHEN MATCHED THEN UPDATE SET CrateID = source.CrateID WHEN NOT MATCHED THEN INSERT (FruitID, CrateID) VALUES (source.FruitID, source.CrateID); 

否则，您可以使用以下内容：

 update [SomeTable] set CrateID = @CrateID where FruitID = @FruitID if @@rowcount = 0 insert [SomeTable] (FruitID, CrateID) values (@FruitID, @CrateID)