Is it possible to write join query without ON statement? and how do these joins differ LEFT JOIN, RIGHT JOIN works.
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MySQL documentation covers this topic.
Here is a synopsis. When using join or inner join, the on condition is optional. This is different from the ANSI standard and different from almost any other database. The effect is a cross join. Similarly, you can use an on clause with cross join, which also differs from standard SQL.
A cross join creates a Cartesian product -- that is, every possible combination of 1 row from the first table and 1 row from the second. The cross join for a table with three rows ('a', 'b', and 'c') and a table with four rows (say 1, 2, 3, 4) would have 12 rows.
In practice, if you want to do a cross join, then use cross join:
from A cross join B
is much better than:
from A, B
and:
from A join B -- with no on clause
The on clause is required for a right or left outer join, so the discussion is not relevant for them.