MySQL数据库操作中常用的一些SQL语句

1.单句SQL语句，从视图中查询结果

select c.product_no, c.product_flag from
(select a.product_flag,b.product_no from product_category as a join product as b on (a.product_category_no=b.product_type)) as c
where c.product_no=8

 

2.根据“年费”查询多个字段

select product_no,product_property_no,product_property_detail_content    from product_property_detail    
    where product_property_name="年费" and (product_property_detail_content between 360 and 500)

 

3.子查询转化“编号”为“名字”

select product_no,product_name,creditcard_rating,
(select bank.bank_name from bank where bank.bank_no=product.company_no)as company_no,product_desc
     from product where product_type=12 and company_no= 2    

 

4.联合查询得详细信息

SELECT
(select product_property_detail_content from product_property_detail where product_no=8 and product_property_no=30) as dhsx,
product_function as jbgn,
((select c.product_flag from (select a.product_flag,b.product_no from product_category as a join product as b on (a.product_category_no=b.product_type)) as c where c.product_no=8 ) )as cplb    
FROM    product where product_no=8

 

5.union操作

select product_no    from product_property_detail    
where product_property_no=3 and (product_property_detail_content between 360 and 500)    
union all
select product_no from product where product_type=12 and company_no= 2    
order by product_no

 

6.多条件查询

select (select product_property_name from product_property as a where a.product_property_no=product_property_detail.product_property_no)
as name,product_property_detail_content as jbgn
from product_property_detail where product_no=8 and    
(product_property_no=1 or product_property_no=13 or product_property_no=14 or product_property_no=15 )

 

7.in语句

select product_no from product where product_no    
in    
(select product_no from product where creditcard_rating="金卡")

 

8.求合集

select * from (select product_no    from product_property_detail    
    where product_property_no=3 and (product_property_detail_content between 360 and 500) ) as a
inner join
(select product_no from product where product_type=12 and company_no= 2 ) as b
on    a.product_no=b.product_no    

 

9.Exists better than In

 背景介绍：product_property_detail表中 product_property_no为种类， product_no为商品标号，他们为多对多关系，主键为： product_property_detail_no，该表只有种类和商品号确定才能找到该唯一的记录号！

测试：找每种种类中商品标号最大的那个商品

方案一：In方式

select product_property_no,product_no,product_name from product_property_detail a
where product_no in (
select max(product_no) from product_property_detail    
where product_property_no = a.product_property_no    
)

结果：

42 rows in set (40.10 sec)

 

方案二：Exists方式

select product_property_no,product_no,product_name from product_property_detail a
where not exists (
select 1 from product_property_detail    
where product_property_no = a.product_property_no and    
product_no > a.product_no
)

结果：

42 rows in set (14.69 sec)

小结：

在查找复杂关系的数据时候Exists会有更好的效率！

本文出自 “专注J2EE系列规范下的开源技术” 博客，请务必保留此出处http://danni505.blog.51cto.com/15547/105616

本文出自 51CTO.COM技术博客