Re: Select * From t1,t2 ON a=b problem

[Rick James]

These patterns are the same:

  FROM a,     b WHERE a.id = b.id
  FROM a JOIN b    ON a.id = b.id

LEFT JOIN lets you get rows from the left table that have no corresponding row in the right table:

  FROM a LEFT JOIN b  ON a.id = b.id
    WHERE b.id IS NULL

Warning. Precedence can be a problem. The first of these is the same as one of the others (depending on the version of MySQL):

  FROM  a, b  JOIN c ON ...
  FROM (a, b) JOIN c ON ...
  FROM  a, (b JOIN c ON ...)