Re: inner join vs left join - huge performance difference
There are a few extra keys that I didn't describe, but here are the EXPLAIN results:
INNER JOIN:
+----+-------------+-------+------------+-------+-----------------+-------+---------+------------+------+----------+------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+-------+-----------------+-------+---------+------------+------+----------+------------------------------------+
| 1 | SIMPLE | table | NULL | range | date,type,LocID | LocID | 6 | NULL | 515 | 9.57 | Using index condition; Using where |
| 1 | SIMPLE | table | NULL | ref | date,type,LocID | LocID | 6 | const,func | 19 | 9.57 | Using index condition; Using where |
+----+-------------+-------+------------+-------+-----------------+-------+---------+------------+------+----------+------------------------------------+
LEFT JOIN:
+----+-------------+-------+------------+-------+-----------------+-------+---------+-------+------+----------+------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+-------+-----------------+-------+---------+-------+------+----------+------------------------------------+
| 1 | SIMPLE | table | NULL | range | date,type,LocID | LocID | 6 | NULL | 527 | 9.57 | Using index condition;Using where |
| 1 | SIMPLE | table | NULL | ref | date,type,LocID | type | 1 | const | 10 | 100.00 | Using where |
+----+-------------+-------+------------+-------+-----------------+-------+---------+-------+------+----------+------------------------------------+
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Re: inner join vs left join - huge performance difference
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