We need subqueries, because somtimes, the question you are trying to answer can't be solved with the set of tables in your database. Instead, there's a need to manipulate existing tables and join them ...

Here we want to show a table including product ids, names, and prices, but only where the price is greater than the average price of products. To get the average price of products, we run a separate ...

I'm trying to port an application from SQL Server to MySQL (5.6.4) and running into performance issues. MySQL happens to be running on OS X Server, but this seems more like a UNIX question. SELECT ...