Read this SQL tutorial to learn when to use SELECT, JOIN, subselects and UNION to access multiple tables with a single statement. It’s sometimes difficult to know which SQL syntax to use when ...

How to Create a Table From Query Results in Microsoft SQL. If your business uses relational databases to store data, you may have used a SQL SELECT clause to create new tables from query results.

When you execute a query using the LEFT JOIN syntax, SQL does two things: It returns all of the records from both tables that contain matching values, as defined by the ON clause.

A join combines two or more tables side by side. If you do not specify how to join the tables, you get a Cartesian product.This means that SQL combines each row from the first table with every row ...

In earlier versions of SQL Server, after selecting a join algorithm, SQL Server had to process it even if a better alternative might be available. In SQL Server 2017, the query optimizer can now sense ...