SQL基础语法——2017.08.29

1 SQL SELECT

select * from lambda.withdrawal_iou_audit_info   //列出lambda.withdrawl_iou_audit_info中所有的列
select withdrawal_id from lambda.withdrawal_detail_info  //选择withdrawal_id字段从lambda.withdrawal_detail_info表

 

2 SQL DISTINCT

DISTINCT:在表中，如果出现重复，需要删选出来的话，直接
select distinct withdrawal_id from withdrawal_detail_info

 

3SQL WHERE

where:有条件的从表中选取数据
SELECT withdrawal_id FROM lambda.withdrawal_detail_info where   withdrawal_id=2 

 

4SQL WHERE 中 AND和OR

AND和OR可在where子语句中把两个或多个条件结合起来
AND:如果第一个条件和第二个条件都成立，则AND运算符显示一条记录
OR：如果第一条件和第二个条件只要有一个成立，则OR运算符显示一条记录

AND:SELECT withdrawal_id FROM lambda.withdrawal_detail_info where  withdrawal_id=2  AND withdrawal_status="APPLYING"

OR:SELECT withdrawal_id FROM lambda.withdrawal_detail_info where  withdrawal_id=2  OR withdrawal_status="APPLYING"

 

5SQL ORDER BY

ORDER BY 语句用于根据指定的列对应结果即进行排序（语句默认为升序进行排列）
如果需要降序排列需要使用DESC关键字，将字段放入最后面

SELECT withdrawal_id FROM lambda.withdrawal_detail_info where   withdrawal_status="APPLYING" ORDER BY withdrawal_amt

 

6SQL INSERT INTO

INSERT INTO 表名称 values（值1，值2，...)

INSERT INTO lambda.withdrawal_detail_info values('Gates','Bill','xuanwumen 10')

　　

7UPDATE语句

UPDATE语句用于修改表中的数据

update 表名 set 列名称=新值 where 列名称=某值

update  Person set  firstname='lin' where lastame='wilson';

　　

8DELETE语句

DELETE语句用于删除表中的行

delete from 表名称 where 列名称=值

delete from lambda.withdrawal_iou_audit_info where  withdrawal_id =2;