WHWRE子句

USE world;            -- 选中数据库,选中加粗
SELECT * FROM city     -- 查询表中所有数据
SELECT * FROM city WHERE ID = 1;         -- 显示表中某行
SELECT DISTINCT Population AS new FROM city;  -- 显示表中某列
-- 如果新名字有空格，需要用引号
-- DISTINCT可以去重
-- AS可以省略

IN运算符

USE world;           
SELECT * FROM country
WHERE Code IN ('ABW','AFG')   
-- 等价于WHERE Code = 'ABW' OR Code = 'AFG'

BETWEEN运算符

USE world;           
SELECT * FROM country
WHERE Population BETWEEN 100000 AND 110000
-- 等同于WHERE Population >= 100000 AND  Population <= 110000

LIKE运算符

两种通配符

• % 任何个数的字符
• _ 单个字符

USE world;           
SELECT * FROM country
WHERE Name LIKE 'Arub%' / 'A___a'

 REGEXP运算符

• ^ 开头
• $ 结尾
• [a-h] 含a-g中任一一个

使用与LIKE相同

USE world;           
SELECT * FROM country
WHERE Name REGEXP 'Arub'

 IS NULL运算符

USE world;           
SELECT * FROM country
where Population is null/is not null

ORDER BY子句

USE world;           
SELECT * FROM country
ORDER BY LifeExpectancy,Region DESC
-- DESC表示降序
-- 可包括任何列 可包括没选择的列
-- 任何一个排序依据列后面都可选加 DESC

LIMIT子句

USE world;           
SELECT * FROM country
limit 3 / 30000 / 6, 3
-- 6，3 表示跳过前6个，取第7~9个，6是偏移量