Why does MySQL report a syntax error on FULL OUTER JOIN?

The Emulation Game: FULL OUTER JOIN in MySQL

MySQL, though robust and popular, sadly does not support FULL OUTER JOIN. However, crafty developers can adeptly wear the hat of a magician and pull out workarounds using other supported JOIN mechanisms. So tie your shoelaces tightly and keep your magic wand ready!

Crafting FULL OUTER JOIN using union

UNION is our magic potion here that combines the results of two or more SELECT statements into a single set. The art of crafting a FULL OUTER JOIN lies in performing individual LEFT JOIN and RIGHT JOIN operations and then sewing them together with a UNION. Be careful about duplicate records while performing the trick though!

Treating NULL values with respect

While performing your magic trick, remember that NULL values are not a disappearance act! They still exist and would pop up in the result of the RIGHT JOIN operation. You need to handle these NULL values with care by including the WHERE table1.id IS NULL clause.

--Getting records with LEFT JOIN
SELECT table1.*, table2.*
FROM table1
LEFT JOIN table2 ON table1.id = table2.id
UNION ALL
--Getting missing records with RIGHT JOIN (handling NULLS like a boss!)
SELECT table1.*, table2.*
FROM table1
RIGHT JOIN table2 ON table1.id = table2.id
WHERE table1.id IS NULL;


Clever use of aliases for complex queries

In the exciting world of MySQL, one often deals with complex queries and multiple tables. In such scenarios, using table aliases is like putting labels on your magic potion bottles to avoid any mishaps.

Practical Scenarios: Where FULL OUTER JOIN shines

FULL OUTER JOIN is like the avenger with a shield and a hammer. You don’t want to negate its power simply because MySQL doesn’t support it natively. So, let’s look at some warzones where FULL OUTER JOIN (emulated, of course) proves to be a superpower!

Analyzing sales and shipment data

Imagine you're a business analyst whose job is to analyze both sales and shipment data. The FULL OUTER JOIN (disguised as a UNION of a LEFT JOIN and a RIGHT JOIN) lets you see sales and their corresponding shipments, while also revealing sales that never shipped and shipments that somehow missed the sales radar.

Complex analysis with multiple tables

When dealing with multiple tables and complex reporting requirements, using LEFT JOIN and RIGHT JOIN operations in parallel, and then combining the outcomes using a UNION clause ensures all possible relationships are analyzed and no data slips between the cracks.

Sparse relationships

Sometimes, two tables have few common keys. In such cases, emulating FULL OUTER JOIN can help build a comprehensive matrix of data capturing all possible key combinations. This solution is like a box of gems for network analytics or gap analysis.