饿虎岗资源网 Design By www.oxmxm.com

参考表:student

MySQL笔记之基本查询的应用详解

多字段查询
复制代码 代码如下:
mysql> select id,name,birth from student;


所有字段查询
复制代码 代码如下:
mysql> select * from student;


where指定查询
复制代码 代码如下:
mysql> select * from student where id=901;
mysql> select * from student where id>=904;
mysql> select name from student where department='计算机系';


in指定集合查询
复制代码 代码如下:
mysql> select * from student where birth in(1988,1990);
mysql> select * from student where id in(903,906);

not in非范围查询
复制代码 代码如下:
mysql> select * from student where birth not in(1990,1998);


between and指定范围查询
复制代码 代码如下:
mysql> select * from student where birth between 1986 and 1988;


not between and不在指定范围的查询
复制代码 代码如下:
mysql> select * from student where id not between 904 and 906;


like字符串匹配查询
复制代码 代码如下:
mysql> select * from student where name like '_三';
mysql> select * from student where name like '张三';
mysql> select * from student where name like '张%';


not like不匹配查询
复制代码 代码如下:
mysql> select * from student where name not like '张%';


null查询
复制代码 代码如下:
mysql> select * from student where address is null;


and多条件查询
复制代码 代码如下:
mysql> select * from student where name like '张%' and birth>1985;
mysql> select * from student where name like '张%' and birth>1985 and id like '%3';


or多条件查询
复制代码 代码如下:
mysql> select * from student where id=905 or birth=1988;
mysql> select * from student where id=905 or birth=1988 or sex='女';

distinct查询结果不重复
复制代码 代码如下:
mysql> select distinct sex from student;
mysql> select distinct department from student;


order by查询结果排序
复制代码 代码如下:
mysql> select * from student order by birth;
mysql> select * from student order by birth asc;
mysql> select * from student order by birth desc;


group by分组查询
复制代码 代码如下:
mysql> select sex,group_concat(name) from student group by sex;
mysql> select sex,count(name) from student group by sex;


正则表达式查询
复制代码 代码如下:
mysql> select * from student where birth regexp '1988|1990';


limit限制查询结果数量
复制代码 代码如下:
mysql> select * from student limit 2;
mysql> select * from student limit 1,3;


饿虎岗资源网 Design By www.oxmxm.com
广告合作:本站广告合作请联系QQ:858582 申请时备注:广告合作(否则不回)
免责声明:本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除!
饿虎岗资源网 Design By www.oxmxm.com

RTX 5090要首发 性能要翻倍!三星展示GDDR7显存

三星在GTC上展示了专为下一代游戏GPU设计的GDDR7内存。

首次推出的GDDR7内存模块密度为16GB,每个模块容量为2GB。其速度预设为32 Gbps(PAM3),但也可以降至28 Gbps,以提高产量和初始阶段的整体性能和成本效益。

据三星表示,GDDR7内存的能效将提高20%,同时工作电压仅为1.1V,低于标准的1.2V。通过采用更新的封装材料和优化的电路设计,使得在高速运行时的发热量降低,GDDR7的热阻比GDDR6降低了70%。

更新日志