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 ...

SQL joins . So far, I’ve described the SELECT syntax for single tables. Before I can explain JOIN clauses, you need to understand foreign keys and relations between tables.

If you only want to update values in table A when there are matching records in table B, then an inner join is the way to go. If you have calculations that need to vary based on optional data, the ...

In this SQL Server tip, Arthur Fuller explains the effects of NULLs, and the different results obtained by inner and outer JOINs.