SQL left join vs multiple tables on FROM line?

Question

Most SQL dialects accept both the following queries:

SELECT a.foo, b.foo
FROM a, b
WHERE a.x = b.x

SELECT a.foo, b.foo
FROM a
LEFT JOIN b ON a.x = b.x
         


        

Answer 1

The first way is the older standard. The second method was introduced in SQL-92, http://en.wikipedia.org/wiki/SQL. The complete standard can be viewed at http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt .

It took many years before database companies adopted the SQL-92 standard.

So the reason why the second method is preferred, it is the SQL standard according the ANSI and ISO standards committee.