Sql updating a table from another table


20-Nov-2017 00:42

If you access a column from the table to be updated in an expression, assignments are generally evaluated from left to right.For multiple-table updates, there is no guarantee that assignments are carried out in any particular order.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. 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.UPDATE My Table SET Column1 = (SELECT Some Column FROM Some Other Table WHERE Such And Such = This And That), Column2 = (SELECT Some Other Column FROM Some Other Table WHERE Such And Such = This And That), ... FROM My Table INNER JOIN Some Other Table ON My Table. This And That WHERE Primary Key Column = Some Value Bear in mind that updating data in one table with data from another table may be a sign of bad database design.

sql updating a table from another table-73

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How to copy values from table A to table B in the same database?

What is the syntax of the SQL UPDATE statement to update field values from one table to another?

Orders AS O GROUP BY O.customer_id )OA ON C.customer_id = OA.customer_id; table while pulling in necessary information from other table(s) referenced in the statement.

If CTEs are your thing, you can even go a step further with this.How to update Columns from one table using data from another with SQL?



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