select distinct col_name from table where a=X and b=Y and date(time)=‘xx-xx-xx‘;
执行时间 27.9772 秒
explain select distinct col_name from table where a=X and b=Y and date(time)=‘xx-xx-xx‘;
id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | |
---|---|---|---|---|---|---|---|---|---|---|
1 | SIMPLE | access | ALL | NULL | NULL | NULL | NULL | 38714243 | Using where; Using temporary |
select distinct col_name from table where a=X and b=Y and time<‘xx-xx-xx‘;
执行时间 0.0038 秒
explain select distinct col_name from table where a=X and b=Y and time<‘xx-xx-xx‘;
id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | |
---|---|---|---|---|---|---|---|---|---|---|
1 | SIMPLE | access | range | idx_access_dt | idx_access_dt | 4 | NULL | 1 | Using where; Using temporary |
select distinct col_name from table where a=X and b=Y and time=‘xx-xx-xx xx:xx:xx‘;
执行时间 0.0031 秒
explain select distinct col_name from table where a=X and b=Y and time=‘xx-xx-xx xx:xx:xx‘;
id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | |
---|---|---|---|---|---|---|---|---|---|---|
1 | SIMPLE | access | ref | idx_access_dt | idx_access_dt | 4 | const | 82 | Using where; Using temporary |
参考:
http://www.cnitblog.com/aliyiyi08/archive/2008/09/09/48878.html
时间: 2024-10-10 00:21:39