UPDATE `WarningSendMail` AS alias_1 INNER JOIN (SELECT * FROM `WarningSendMail` WHERE flag=1 AND topic_id LIKE "%2267%") AS alias_2 SET alias_1.topic_id = REPLACE(alias_1.topic_id,‘|2267‘,‘‘) WHERE alias_1.id = alias_2.idupdate WarningSendMail set topic_id= REPLACE(topic_id,‘|2267‘,‘‘) WHERE id IN ( SELECT id FROM WarningSendMail WHERE flag=1 AND topic_id LIKE "%2267%" );Mysql下SELECT的结果...
grant all on *.* to root@‘%‘ identified by ‘123‘; Query OK, 0 rows affected (0.00 sec) 授权用户后参看mysql> select user,host from mysql.user where user like ‘root‘; +------+-----------+ | user | host | +------+-----------+ | root | % | | root | 10.0.0.1 | | root | 127.0.0.1 | | root | localhost | +------+-----------+ 4 rows in set (0.00 sec)1.1.2 select语法格式说明mysql> help...
9.9.8 查询数据 9.9.8.1 查询表的所有数据行 (1)命令语法:select<字段1,字段2,…>from<表名>where<表达式> (2)列子:查看表wwn中所有数据 a.进入指定数据库查询 system@ceshi 04:5152->use wwn Database changed system@ceshi 04:5159->select * from test -> ; +----+-----------+ | id | name | +----+-----------+ | 1 | wwnwan| | 2 | zbf | | 3 | lisi | | 4 | woshishei | | 5 | nimei | +----+---------...
说明:SELECT命令可以实现多组记录的查询,其中“*”表示列出指定表的所有内容; WHERE用来设定查询条件; LIMIT用来限制输出的记录数量; OFFSET指定SELECT语句开始查询的数据偏移量,默认情况下值为0。 实例一:输出table的所有内容mysql> select * from courses; +-----+--------+-----------------+ | num | name | submission_date | +-----+--------+-----------------+ | 1 | ...
+----+----------+-------+ | id | name | slary | +----+----------+-------+ | 1 | guoding | 3200 | | 2 | dingtao | 2800 | | 3 | haofugui | 3500 | | 4 | guoming | 4000 | | 5 | haotian | 2900 | | 6 | fengfei | 3200 | | 7 | guoting | 2600 | +----+----------+-------+ 7 rows in set (0.00 sec)mysql> select * from staff_1; +----+----------+-------+ | id | name | slary | +----+--...
Query OK, 0 rows affected (0.11 sec)mysql> insert into Total (name,stu_num,teacher_num) values ("小学1",400,20),("小学2",356,24),("小学3",403,19),("小学4",367,26),("小学5",373,20),("小学6",406,21); Query OK, 6 rows affected (0.00 sec) Records: 6 Duplicates: 0 Warnings: 0mysql> select * from Total; +----+---------+---------+-------------+ | id | name | stu_num | teacher_num | +----+---------+-...
之前用SqlServer , update语句对表进行更新:update a set a.xx= (select yy from b) ; 是可以的但是在mysql中,不能直接使用set select的结果, UPDATE ecs_users_copySET `user_name` = ( SELECT `identity_card` FROM ecs_users_copy WHERE LENGTH(identity_card) = 18 AND LENGTH(user_name) != 18 ) 这是错误的做法! 必须使用inner join: demo1update a inner join (select table from b) c set a.id = a.id where a xx...
礼悟: 公恒学思合行悟,尊师重道存感恩。叶见寻根三返一,江河湖海同一体。 虚怀若谷良心主,愿行无悔给最苦。读书锻炼养身心,诚劝且行且珍惜。 数据、数据,命根就在数据。操作数据库一定要谨慎小心。给最苦 这里的代码,看看就好,要有自己的判断。遇到抉择,要不耻上下问。 mysql:5.7 os:Windows7 x64 代码及效果mysql> select * from t1; +------+-------+ | id...
礼悟: 公恒学思合行悟,尊师重道存感恩。叶见寻根三返一,江河湖海同一体。 虚怀若谷良心主,愿行无悔给最苦。读书锻炼养身心,诚劝且行且珍惜。 数据、数据,命根就在数据。操作数据库一定要谨慎小心。给最苦 这里的代码,看看就好,要有自己的判断。遇到抉择,要不耻上下问。 mysql:5.7 os:Windows7 x64 代码及效果mysql> select * from t1; +------+-------+ | id...
select * from t1; +------+-------+ | id | name | +------+-------+ | 4 | Hello | | 2 | World | | 1 | nihao | | 3 | nihao | | 100 | nihao | +------+-------+ 5 rows in set (0.00 sec) 只看其中的一列mysql> select name from t1; +-------+ | name | +-------+ | Hello | | World | | nihao | | nihao | | nihao | +-------+ 5 rows in set (0.00 sec) mysql,关系型数据库管理系统,优秀,...
desc t1; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | name | varchar(10) | YES | | 未登记 | | +-------+-------------+------+-----+---------+-------+ 2 rows in set (0.02 sec)mysql> select * from t1; +------+----...
select * from t1; +------+-------+ | id | name | +------+-------+ | 4 | Hello | | 2 | World | | 1 | nihao | | 3 | nihao | | 100 | nihao | +------+-------+ 5 rows in set (0.00 sec)mysql> select * from t1 order by id asc; +------+-------+ | id | name | +------+-------+ | 1 | nihao | | 2 | World | | 3 | nihao | | 4 | Hello | | 100 | nihao | +------+-------+ 5 rows in s...
* from staff; +----+----------+-------+ | id | name | slary | +----+----------+-------+ | 3 | haofugui | 10000 | | 4 | guoming | 3500 | | 5 | haotian | 2900 | +----+----------+-------+ 3 rows in set (0.00 sec)mysql> describe staff; +-------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+--...
<?php$mysqli = new Mysqli();$mysqli->connect("localhost","root","root","test");if ( $mysqli->connect_errno ){die( $mysqli->connect_error );}$mysqli->set_charset("utf8");$sql = "select * from mysqli;";$mysqli_result = $mysqli->query($sql);if( ! $mysqli_result ){echo "error:".$mysqli->errno." : ".$mysqli->error;} else {print_r( $mysqli_result ); //打印查看会是一个mysqli_result对象}$mysqli->close(); ...
MySQL select * 和把所有的字段都列出来,哪个效率更高 答案是:如何,都不推荐使用 SELECT * FROM (1)SELECT *,需要数据库先 Query Table Metadata For Columns,一定程度上为数据库增加了负担。 但是实际上两者效率差别不大。 (2)考虑到今后的扩展性 因为程序里面你需要使用到的列毕竟是确定的, SELECT * 只是减少了一句 SQL String 的长度,并不能减少其他地方的代码。MySQL select * 和把所有的字段都列出来,哪个效率更高...