Sql updating a table with values from another table about love and dating
In fact, I struggled with this problem for quite some time before I found out about this gem.
In the following lines, I am going to show you three tricks that have made my life simpler on many occasions.
Customers AS C JOIN( SELECT O.customer_id, COUNT(1) cnt FROM dbo.
Orders AS O GROUP BY O.customer_id )OA ON C.customer_id = OA.customer_id; UPDATE C SET /* SELECT *, -- */ order_count = FROM dbo.
Use the @@ROWCOUNT function to return the number of inserted rows to the client application. If ANSI_PADDING is set to OFF, all trailing spaces are removed from data inserted into varchar and nvarchar columns, except in strings that contain only spaces. If ANSI_PADDING is set to ON, trailing spaces are inserted.For that, we first need two tables: If you want to follow along, you can get the script here: The Hidden SQL Server Gem - UPDATE from Now that we have the environment set up, let's dive into how to make this work.Before I show you the multi-table solution, let me demonstrate the simplest form of the --UPDATE C SET /* SELECT *, -- */ order_count = FROM dbo.As long as SQL Server can easily determine what you are intending to update, you can actually "UPDATE" a CTE directly using a very similar syntax: WITH order_counts AS ( SELECT O.customer_id, COUNT(1) cnt FROM dbo.Orders AS O GROUP BY O.customer_id ), customer_order_counts AS ( SELECT C.customer_id, C.name, C.order_count, new_order_cnt FROM dbo.
The search condition can also be the condition upon which a join is based.