The Basics of SQL Joins in MySQL

“When making your first forays into relational database
development, you can use simple SQL statements to mine your data
easily enough. However, as your data grows in both size and
breadth, you’ll need to begin employing more sophisticated
strategies for exploiting increasingly complex data relations.
After all, pulling data from a single table is easy, but what if
you need to query for data spanning three, four, or even eight
different tables?

“Retrieving interrelated data stored within multiple tables is
most effectively accomplished using a SQL JOIN clause, of which
there are several variants. The JOIN clause relies upon related
fields found in two tables to determine the commonality of the data
stored within each, producing a data set that you can then easily
save or further manipulate.

“In this article, I introduce three of the most commonly used
JOIN variants: the INNER JOIN, OUTER JOIN, and SELF JOIN, and
provides MySQL examples for using them. Although these examples
will be MySQL-specific, you’ll be able to use what you learn here
within most — if not all — other relational database
solutions.”

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