1.SELECT和条件查询

select 是强大而复杂的查询语句，深入掌握select查询，就相当于掌握了SQL注入的精髓。(1)如何查询用户表的所有记录 SELECT from users (2)条件查询 SELECT FROM users where uname=’admin’ and password=’abc123’;#### 2.SELECT排序、限制和子查询 (1)排序和限制 正序 SELECT FROM users order by uid 倒序 SELECT FROM users order by uid desc 按第三列排序 SELECT FROM users order by 3 取前10行 SELECT FROM users order by 3 limit 10

(2)子查询 SELECT * FROM users where id in(SELECT uid FROM admin)

SELECT * FROM users where exists(SELECT uid FROM admin)#### 3.SELECT连接查询 (1)左连接 返回a表的所有记录和b表中与a表uid匹配的记录 SELECT a.uname,b.mobile FROM game_user a left JOIN game_user_ext b ON a.uid=b.uid

(2)右连接 返回b表所有记录和a表中与b表uid匹配的记录 SELECT a.uname,b.mobile FROM game_user a right JOIN game_user_ext b ON a.uid=b.uid

(3)内连接 返回a表uid与b表uid匹配，同时存在a表和b表的匹配记录 SELECT a.uname,b.mobile FROM game_user a inner JOIN game_user_ext b ON a.uid=b.uid