MYsql 之单标查询.

http://www.cnblogs.com/wangfengming/articles/8064956.html

.数据操作

    .增
        INSERT into t2(name,age) VALUES('小三',); -- 指定字段插入

        INSERT into t2 VALUES('凤',,2.5); -- 整表字段插入

        INSERT into t2 VALUES('凤',,2.5),('凤',,2.5),('凤',,2.5),('凤',,2.5),('凤',,2.5);
        --插入多条
        insert into t1 SELECT id,name from t2; -- 复制表数据
    .删
        delete from t2 where age = ;
    .改
        update t2 set name ='祝小凤' , salary =  where age =;
    .查
        select * from T1;

        .简单查询
            -- 查询所有
            select * from person;
            --查询指定字段
            select name,age FROM person;
            -- 别名+字段运算
            select p.name,p.salary,p.salary+p.salary*0.1 as 'sum' from person as p
            -- 去重复查询
            select DISTINCT salary,name from person; 

        .条件查询
            -- 逻辑运算符 < > <= >= != <> =
            -- is null ,is not null
            -- and  OR ()

            SELECT * from person where salary > or ( age <= AND NAME ='');

        .区间查询
            SELECT * FROM person where salary >= and salary<=;
            -- 推荐使用 :
            --ps:前后包含

            SELECT * FROM person where salary between  and ;

        .集合查询 in not in

            SELECT * FROM person where age =  or age =  or age = ;

            SELECT * FROM person where age not in(,,);

        .模糊查询 like
            SELECT * FROM person where name LIKE '%月'; -- 以什么结尾

            SELECT * FROM person where name LIKE '月%'; -- 以什么开头

            SELECT * FROM person where name LIKE '%月%'; -- 包含

            SELECT * FROM person where name LIKE '_l%'; -- "_"表示占位符

        .排序
            select * from person ORDER BY salary ASC,age desc;

            -- 强制中文[排序
            select * FROM person ORDER BY CONVERT(name USING GBK) ;

        .聚合函数
            select MAX(salary) from person;
            select MIN(salary) from person;
            select AVG(salary) from person;
            select SUM(salary) from person;
            select COUNT(*) from person;

        .分组查询   GROUP BY  HAVING
            select count(id),dept_id,avg(salary) from person GROUP BY dept_id HAVING avg(salary) >= ;
             where 与 having区别:
            #执行优先级从高到低：where > group by > having
            #. Where 发生在分组group by之前，因而Where中可以有任意字段，但是绝对不能使用聚合函数。
            #. Having发生在分组group by之后，因而Having中可以使用分组的字段，无法直接取到其他字段,可以使用聚合函数

        .分页查询 LIMIT
            SELECT * FROM person LIMIT ,

        .正则表达式
            SELECT * FROM person where name REGEXP '^a';

            SELECT * FROM person where name REGEXP 'n$';

            SELECT * FROM person where name REGEXP '.a';

            SELECT * FROM person where name REGEXP '[a,e,n]';

            SELECT * FROM person where name REGEXP '[^alex]';

            SELECT * FROM person where name REGEXP 'a|e';

            SELECT * FROM person where name REGEXP '^w.*i$';

        . SQL 语句关键字的执行顺序

            执行顺序: FROM -> WHERE -> GROUP BY -> HAVING -> SELECT -> ORDER BY ->limit