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SQL code:
explain select * from t_user where username like '%ÅÖ';

½á¹û:
+----+-------------+--------+-------+---------------+------------+---------+------+------+-----------------------
| id | select_type | table  | type  | possible_keys | key        | key_len | ref  | rows | Extra
           
+----+-------------+--------+-------+---------------+------------+---------+------+------+-----------------------
|  1 | SIMPLE      | t_user | index | NULL          | ind_second | 62      | NULL |    5 | Using where; Using

index |

possible_keys ÊÇ¿ÉÓõÄË÷Òý£¬key ÊÇÓõ½µÄË÷Òý
possible_keys Ϊnull ,key ¾Í²»¿ÉÄÜÓÐֵѽ

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show index from t_user;
show create table t_user;

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show index from t_user;
show create table t_user;

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CREATE TABLE `t_user` (
  `userid` int(11) NOT NULL AUTO_INCREMENT,
  `userName` varchar(20) NOT NULL,
  PRIMARY KEY (`userid`),
  KEY `ind_second` (`userName`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=