Although tables in SQL databases typically contain massive amounts of data, they’re not always in a format that can be used by data analysts. The data records in these tables need to be filtered ...

The indexes on a the tables of a large database make a huge difference in its performance and utility. Without an index, locating a single record in a large table can take several seconds; with the ...

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 ...

A common SQL habit is to use SELECT * on a query, because it’s tedious to list all the columns you need. Plus, sometimes those columns may change over time, so why not just do things the easy way? But ...