h5响应式网站制作,长沙短视频制作,网站推广排名怎么做,网站建设与制作设计公司1、使用SHOW语句找出在服务器上当前存在什么数据库#xff1a;mysql SHOW DATABASES;2、创建一个数据库MYSQLDATAmysql CREATE DATABASE MYSQLDATA;3、选择你所创建的数据库mysql USE MYSQLDATA; (按回车键出现Database changed 时说明操作成功#xff01;)4、查…1、使用SHOW语句找出在服务器上当前存在什么数据库mysql SHOW DATABASES;2、创建一个数据库MYSQLDATAmysql CREATE DATABASE MYSQLDATA;3、选择你所创建的数据库mysql USE MYSQLDATA; (按回车键出现Database changed 时说明操作成功)4、查看现在的数据库中存在什么表mysql SHOW TABLES;5、创建一个数据库表mysql CREATE TABLE MYTABLE (name VARCHAR(20), sex CHAR(1));6、显示表的结构mysql DESCRIBE MYTABLE;7、往表中加入记录mysql insert into MYTABLE values (”hyq”,”M”);8、用文本方式将数据装入数据库表中(例如D:/mysql.txt)mysql LOAD DATA LOCAL INFILE “D:/mysql.txt” INTO TABLE MYTABLE;9、导入.sql文件命令(例如D:/mysql.sql)mysqluse database; mysqlsource d:/mysql.sql;10、删除表mysqldrop TABLE MYTABLE;11、清空表mysqldelete from MYTABLE;12、更新表中数据mysqlupdate MYTABLE set sex”f” where name’hyq’;匿名帐户删除、 root帐户设置密码:use mysql; delete from User where User”; update User set PasswordPASSWORD(’newpassword’) where User’root’;GRANT的常用用法如下grant all on mydb.* to NewUserNameHostName identified by “password” ; grant usage on *.* to NewUserNameHostName identified by “password”; grant select,insert,update on mydb.* to NewUserNameHostName identified by “password”; grant update,delete on mydb.TestTable to NewUserNameHostName identified by “password”;全局管理权限FILE: 在MySQL服务器上读写文件。PROCESS: 显示或杀死属于其它用户的服务线程。RELOAD: 重载访问控制表刷新日志等。SHUTDOWN: 关闭MySQL服务。数据库/数据表/数据列权限ALTER: 修改已存在的数据表(例如增加/删除列)和索引。CREATE: 建立新的数据库或数据表。DELETE: 删除表的记录。DROP: 删除数据表或数据库。INDEX: 建立或删除索引。INSERT: 增加表的记录。SELECT: 显示/搜索表的记录。UPDATE: 修改表中已存在的记录。特别的权限ALL: 允许做任何事(和root一样)。USAGE: 只允许登录–其它什么也不允许做。MySQL-Practice-Questions1、取得每个部门最高薪水的人员名称第一步取得每个部门最高薪水『按照部门分组求最大值』mysql select deptno,max(sal) as maxsal from emp group by deptno;deptnomaxsal105000.00203000.00302850.00第二步将上面的查询结果当作临时表tt表和emp e表进行连接条件e.deptnot.deptno and e.salt.salmysql select - e.ename t.* - from - emp e - join - (select deptno,max(sal) as maxsal from emp group by deptno) t - on - e.deptnot.deptno and e.sal t.maxsal;enamedeptnomaxsalBLAKE302850.00SCOTT203000.00KING105000.00FORD203000.002、那些人的薪水在部门的平均薪水之上第一步找出部门的平均薪水『按部门编号分组求平均薪水』select deptno,avg(sal) as avgsal from emp group by deptno;deptnoavgsal102916.666667202175.000000301566.666667第二步将上面的查询结果当作临时表t与emp e表进行连接 条件t.deptnot.deptno and e.sal t.avgsalselect e.ename,e.sal,t.* from emp e join (select deptno,avg(sal) as avgsal from emp group by deptno) t on e.deptnot.deptno and e.sal t.avgsal;enamesaldeptnoavgsalALLEN1600.00301566.666667JONES2975.00202175.000000BLAKE2850.00301566.666667SCOTT3000.00202175.000000KING5000.00102916.666667FORD3000.00202175.0000003、1取得部门中(所有人)平均薪水的等级第一步取得部门中的平均薪水select deptno,avg(sal) as avgsal from emp group by deptno;deptnoavgsal102916.666667202175.000000301566.666667第二部将上面的查询结果当作临时表tt表和salgrade s表进行关联 条件e.sal between s.losal and s.hisalselect t.*,s.grade from salgrade s join (select deptno,avg(sal) as avgsal from emp group by deptno) t on t.avgsal between s.losal and s.hisal;deptnoavgsalgrade102916.6666674202175.0000004301566.66666733、2取得部门中(所有人)薪水的平均等级第一步每个员工的薪水等级(oder by 以部门编号排序为了好理解)select e.ename,e.sal,e.deptno,s.grade from emp e join salgrade s on e.sal between s.losal and s.hisal ;enamesaldeptnogradeMILLER1300.00102KING5000.00105CLARK2450.00104ADAMS1100.00201SCOTT3000.00204FORD3000.00204JONES2975.00204SMITH800.00201MARTIN1250.00302ALLEN1600.00303JAMES950.00301BLAKE2850.00304WARD1250.00302TURNER1500.00303第二步在以上基础上继续以部门编号分组求平均薪水等级select e.deptno,s.grade from emp e join salgrade s on e.sal between s.losal and s.hisal group by e.deptno;deptnograde1042013034、不用组函数(MAX),取得最高薪水(给出两种解决方案)方案一按照薪水降序排取得第一个mysql select sal from emp order by sal desc limit 1;方案二自连接mysqlmysql select sal from emp where sal not in(select a.sal from emp a join emp b on a.sal b.sal);sal5000.005、取得平均薪水最高的部门的编号(至少给出两种解决方案)第一种方案平均薪水降序排取第一个 第一步取得每个部门的平均薪水mysql select deptno,avg(sal) avgsal from emp group by deptno;deptnoavgsal102916.666667202175.000000301566.666667第二步取得平均薪水的最大值mysql select avg(sal) avgsal from emp group by deptno order by avgsal desc limit 1;avgsal2916.666667第三步将第一步和第二步结合select deptno,avg(sal) as avgsal from emp group by deptno having avg(sal)( select avg(sal) avgsal from emp group by deptno order by avgsal desc limit 1);deptnoavgsal102916.666667第二种方案MAX函数select deptno,avg(sal) as avgsal from emp group by deptno having avg(sal)( select max(t.avgsal) from (select avg(sal) avgsal from emp group by deptno) t);deptnoavgsal102916.6666676、取得平均薪水最高的部门的部门名称select d.dname,avg(e.sal) as avgsal from emp e join dept d on e.deptnod.deptno group by d.dname having avg(e.sal)( select max(t.avgsal) from (select avg(sal) avgsal from emp group by deptno) t);dnameavgsalACCOUNTING2916.666667