Which is the best practice to write sql - sql

Question

Below two queries give same results.
Just wanted to know which one is better in terms of performance.
Query 1:
SELECT N.*
FROM NOTIFICATIONS N
JOIN NOTIFICATION_COMPANY_GROUPS NCG
ON ( N.COMPANY_ID = NCG.COMPANY_ID
AND N.ID = NCG.NOTIFICATION_ID )
JOIN COMPANY_USER_GROUPS CUG
ON ( N.COMPANY_ID = CUG.COMPANY_ID
AND CUG.COMPANY_GROUP_ID = NCG.COMPANY_GROUP_ID )
JOIN NOTIFICATION_PROPERTIES NP ON ( N.COMPANY_ID = NP.COMPANY_ID )
JOIN COMPANY_USER_PROPERTIES CUP
ON ( N.COMPANY_ID = CUP.COMPANY_ID
AND CUP.PROPERTY_ID = NP.PROPERTY_ID )
WHERE N.COMPANY_ID = 2138
AND CUG.COMPANY_USER_ID = 41422
AND CUP.COMPANY_USER_ID = 41422;
Query 2:
SELECT N.*
FROM NOTIFICATIONS N
JOIN NOTIFICATION_COMPANY_GROUPS NCG
ON ( N.COMPANY_ID = 2138
AND N.COMPANY_ID = NCG.COMPANY_ID
AND N.ID = NCG.NOTIFICATION_ID )
JOIN COMPANY_USER_GROUPS CUG
ON ( CUG.COMPANY_USER_ID = 41422
AND N.COMPANY_ID = CUG.COMPANY_ID
AND CUG.COMPANY_GROUP_ID = NCG.COMPANY_GROUP_ID )
JOIN NOTIFICATION_PROPERTIES NP ON ( N.COMPANY_ID = NP.COMPANY_ID )
JOIN COMPANY_USER_PROPERTIES CUP
ON ( CUP.COMPANY_USER_ID = 41422
AND N.COMPANY_ID = CUP.COMPANY_ID
AND CUP.PROPERTY_ID = NP.PROPERTY_ID );

Answer 1

I expect the performance should be the same, but you can use EXPLAIN to verify that the query plan is the same.
However, the first version is the "proper" way to write it. Generally, ON clauses should only contain conditions that relate the tables being joines, while conditions on single tables should be in WHERE clauses.
The only exception to this is in LEFT JOIN clauses, where conditions on the table being joined should be in the ON clause. This is because if you put them in the WHERE clause, the null rows from rows in the main table that have no matches in the joining table will be filtered out unless you explicitly check for NULL. As an example:
SELECT ...
FROM T1
LEFT JOIN T2 ON T2.T1_id = T1.id AND T2.someCol = 3
versus
SELECT ...
FROM T1
LEFT JOIN T2 ON T2.T1_id = T1.id
WHERE T2.someCol = 3
In the first version, the test of T2.someCol is done before joining; the result will contain all rows from T1, but the ones with no matching row in T2 will have NULL for all the T2 columns. But the second version won't have any of these non-matching rows, because the join is done first, and then it performs the T2.someCol = 3 test; if there was no matching T2 row, T2.someCol will be NULL, and this test will fail and the row will be filtered out by WHERE.
In the case of an inner join, it doesn't matter whether you do the comparison before or after joining, the results are equivalent. The query planner should order these in whichever way takes best advantage of indexes.