PHP tips by a MYSQL DBA
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PHP tips by a MYSQL DBA
- 14. Slow-query log II The explain plan shows as below: id: 1 select_type: SIMPLE table: ClientFeedback_backup type: ref possible_keys: SentIndex,CompanyMobileIndex key: SentIndex key_len: 2 ref: const rows: 434148 Extra: Using where; Using temporary; Using filesort
- 35. Use MySQL variables mysql> set @count:= 0; Query OK, 0 rows affected (0.00 sec) mysql> select @count:= @count + 1 as myid, p from t; +------+-----+ | myid | p | +------+-----+ | 1 | 20% | | 2 | 20% | | 3 | 30% | | 4 | 30% | | 5 | 50% | | 6 | 50% | +------+-----+ 10 rows in set (0.00 sec)
- 40. Forget select * mysql> explain select * from tbl_compcatarea a inner join bid_details b on a.contactid=b.contractid; +----+-------------+-------+------+---------------+-----------+---------+--------------------+-------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+-----------+---------+--------------------+-------+-------+ | 1 | SIMPLE | b | ALL | ContractID | NULL | NULL | NULL | 24386 | | | 1 | SIMPLE | a | ref | contactid | contactid | 47 | d_jds.b.contractID | 1 | | +----+-------------+-------+------+---------------+-----------+---------+--------------------+-------+-------+ mysql> explain select a.contactid, a.compname from tbl_compcatarea a inner join bid_details b on a.contactid=b.contractid; +----+-------------+-------+-------+---------------+------------+---------+--------------------+-------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+---------------+------------+---------+--------------------+-------+-------------+ | 1 | SIMPLE | b | index | ContractID | ContractID | 48 | NULL | 24386 | Using index | | 1 | SIMPLE | a | ref | contactid | contactid | 47 | d_jds.b.contractID | 1 | | +----+-------------+-------+-------+---------------+------------+---------+--------------------+-------+-------------+