浅谈MySQL数据库优化

mysql> explain select * from test where id/2<100\G; 
*************************** 1. row *************************** 
id: 1 
select_type: SIMPLE 
table: test 
type: ALL 
possible_keys: NULL 
key: NULL 
key_len: NULL 
ref: NULL 
rows: 1534755 
Extra: Using where 
1 row in set (0.78 sec) 

ERROR: 
No query specified 

mysql> explain select * from test where id<100*2\G; 
*************************** 1. row *************************** 
id: 1 
select_type: SIMPLE 
table: test 
type: range 
possible_keys: idx_test 
key: idx_test 
key_len: 4 
ref: NULL 
rows: 16296 
Extra: Using where 
1 row in set (0.09 sec) 

ERROR: 
No query specified