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Netty核心原理剖析与RPC实践0--5

Villagers 2天前 阅读 2
-- DQL 数据库查询语言
SELECT * FROM employee5;
SELECT DISTINCT(post) FROM employee5;  -- 去重
SELECT now(); -- 查询当前时间
SELECT DATABASE(); -- 查询当前数据库
SELECT user(); -- 查询当前登录的用户
SELECT SLEEP(10); -- 停滞10秒
SELECT 12455175195159 / 1024 / 1024 / 1024;
SELECT 10 > 5;
SELECT `name`,salary * 16 FROM employee5;-- 计算所有员工的年薪
SELECT CONCAT(`name`,'-',sex) as name_sex FROM employee5; -- 拼接字段,并修改临时列名
SELECT * from employee5 WHERE sex="male"; -- 查询所有的男生
SELECT * FROM employee5 WHERE sex="male" and salary >= 5500; -- 查询薪资大于等5500的男生
SELECT * FROM employee5 WHERE office = '501' or salary > 10000;     -- 查询在501办公室或薪资大于10000以上的员工
SELECT * FROM employee5 WHERE salary > 6000 and salary < 10000; -- 薪资大于6000且小于10000的员工
SELECT * FROM employee5 WHERE salary BETWEEN 6000 AND 10000; -- 薪资大于6000且小于10000的员工,在两者之间
SELECT * FROM employee5 WHERE job_description is not NULL; -- 判断是否为空
SELECT * FROM employee5 WHERE office in (501,503);-- 查询所有在501和503 办公室的员工
SELECT * FROM employee5 ORDER BY salary asc  -- 查询薪资,升序
SELECT * FROM employee5 ORDER BY salary desc -- 查询薪资,降序
SELECT * from employee5 LIMIT 5; -- 分页,查看前5条
SELECT * from employee5 LIMIT 2,5;  -- 第几条之后,数几条
SELECT sex,GROUP_CONCAT(`name`) FROM employee5 GROUP BY sex; -- 分组查询
SELECT * FROM employee5 WHERE `name` LIKE "%m%"; -- 查询名字中带有m的员工
SELECT COUNT(*) FROM employee5; -- 一共有多少条数据被查询
SELECT avg(salary) FROM employee5;-- 工作最高的员工max 最低的员工min 平均值avg
SELECT sum(salary) FROM employee5;
SELECT password("QianFeng@111");  -- 密码加密
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