Without theORDER-BYclause, the order in which the selected lines are supplied is undefined. This means that two similarSELECTstatements may produce lines in a different order. Variant 1 ...ORDER BY PRIMARY KEY Effect Sorts the selected lines in ascending order by the___of the database...
PRIMARY KEY ( `id`), INDEX idx_city ( `city` ) ) ENGINE = INNODB COMMENT '员工表'; 表数据如下: 我们现在有这么一个需求:查询前10个,来自深圳员工的姓名、年龄、城市,并且按照年龄小到大排序。对应的 SQL 语句就可以这么写: select name,age,city from staff where city = '深圳' order by age ...
.. order by primary key?Posted by: Mihsah Nahk Date: June 11, 2009 05:08AM Hi! I have a table called myTable with a primary key consisting of the columns (datum, tid). However, when I make a select statement from the myTable and order by the primary key, the primary key ...
数据库默认是不开启profiling的,变量profiling是用户变量,每次都得通过set profiling=1;重新启用,可以通过set profiling=0关闭。 1.添加PRIMARY KEY(主键,聚簇索引) mysql>ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` ) 2.添加UNIQUE(unique表示该字段的值唯一,这种约束需要通过建立唯一索引实现的,所以这...
order by 走不走索引 order by索引原理,一、抛砖引玉现有表结构如下:CREATETABLE`t`(`id`int(11)NOTNULL,`city`varchar(16)NOTNULL,`name`varchar(16)NOTNULL,`age`int(11)NOTNULL,`addr`varchar(128)DEFAULTNULL,PRIMARYKEY(`i
PRIMARY KEY (`id`) USING BTREE, INDEX`idx_title_name_price`(`hero_title`,`hero_name`,`price`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT =11CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic; -- --- -- Records of t_lol -- --- INSERT...
PRIMARY KEY (`id`), KEY `user_id` (`user_id`) ) ENGINE=InnoDB; 表中目前有两个点需要关注下: 用户的 user_id ,朋友的姓名 friend_name 、朋友的地址 friend_addr user_id 是有 索引 的 有一天,有个初级开发工程师小猿,收到了来自初级产品经理小汪的需求: ...
CREATE TABLE `student` (`id` int(11) NOT NULL AUTO_INCREMENT,`stuno` int(11) NOT NULL,`name` varchar(20) DEFAULT NULL,`age` int(3) DEFAULT NULL,`classId` int(11) DEFAULT NULL,PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=500001 DEFAULT CHARSET=utf8; ...
( 11 ) AUTO_INCREMENT COMMENT '主键id', `id_card` VARCHAR ( 20 ) NOT NULL COMMENT '身份证号码', `name` VARCHAR ( 64 ) NOT NULL COMMENT '姓名', `age` INT ( 4 ) NOT NULL COMMENT '年龄', `city` VARCHAR ( 64 ) NOT NULL COMMENT '城市', PRIMARY KEY ( `id`), INDEX idx_...
CREATETABLE`student`(`id`int(11)NOTNULLAUTO_INCREMENT,`name`varchar(11)DEFAULT'',`age`int(11)DEFAULT'0',`classId`int(11)DEFAULT'0',PRIMARYKEY(`id`))ENGINE=InnoDBAUTO_INCREMENT=10000DEFAULTCHARSET=utf8; 存储过程插入1w条数据: 代码语言:javascript ...