how can i update SQL table logic

Question

I have a table structured as,

Table 3

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

Now

Answer 1

You can do an "upsert" with the MERGE syntax in SQL Server:

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);

Otherwise, you can use something like:

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