MySQL JOIN behind the scenes

I remember reading somewhere / being told / inventing a rumor 开发者_如何学编程(^_^) that the two following queries are the same behind the scenes in MySQL servers:

SELECT *
FROM a
JOIN b
ON a.id = b.id

and

SELECT *
FROM a, b
WHERE a.id = b.id

Is it true? If so, is one better than the alternate in other terms? (such as parsing efficiency or standard compliance)

It is in fact true. The first query is according the SQL-89 standard and the second is according to SQL-92.

The SQL-92 standard introduced INNER JOIN .. ON and OUTER JOIN .. ON in order to replace the more complex(?) syntax of SQL-89.

An outer join in SQL-89 would be:

SELECT ...
FROM t1, t2
WHERE t1.id *= t2.id

where in SQL-92 it would be

FROM t1 OUTER JOIN t2 ON t1.id = t2.id

I did prefer SQL-89 over SQL-92 for a long while, but I think SQL Server 2008 compability removed the support for SQL-89 join syntax.

yep, these are identical. But it's not something specific to Mysql - it's just a different joining styles. The one you wrote on top is newer and preffered one