今天遇到數據庫的一個更新操作.
1個數據庫中有兩個表(其中一個表是從另一個數據庫複製來的,方法見我以前文章),這兩個表通過公司名稱對應起來,其中一個有稱謂(Mr.,Miss.,Mrs),另一個沒有,將這個表的稱謂導入到另一個表中:
sql: update tb_company set tb_company.Salutation1=tb_companyorg.Title from tb_company,tb_companyorg where tb_company.CompanyName_eng=tb_companyorg.Company_name
此sql語句作用爲:將tb_companyorg表的Title(稱謂)導入到tb_company表的Salutation1(稱謂)字段中,通過兩表的公司名稱進行對應,一次性導入了17w+條數據
參考link:http://www.cnblogs.com/ywkpl/archive/2008/03/11/1101276.html
參考內容:
Product(pid,name,amount,nowAmount):標識,名稱,已有數量,當前數量
Trade(id,pid,operType,number):標識,產品標識,操作類型(入庫:1,出庫:0),數量
Product表中測試數據:
1 | 蘋果 | 100 | 0 |
2 | 桔子 | 50 | 0 |
Trade表中測試數據:
1 | 1 | 1 | 432 |
2 | 1 | 0 | 50 |
3 | 2 | 1 | 20 |
4 | 2 | 0 | 40 |
5 | 1 | 1 | 30 |
6 | 2 | 0 | 20 |
現要求一條SQL語句更新Product表中nowMount值
語句如下:
update p set p.nowAmount = p.amount+t.number
from Product as p ,(select pid,sum(case operType when '0' then number* (-1) else number end) number
from Trade group by pid) as t where t.pid=s.pid
from Product as p ,(select pid,sum(case operType when '0' then number* (-1) else number end) number
from Trade group by pid) as t where t.pid=s.pid
或者
update p
set p.nowAmount= t.number+p.amount
from Product as p
inner join (select pid ,sum(case operType when '0' then number* (-1) else number end) as number from Trade group by pid) as t
on p.pid=t.pid
set p.nowAmount= t.number+p.amount
from Product as p
inner join (select pid ,sum(case operType when '0' then number* (-1) else number end) as number from Trade group by pid) as t
on p.pid=t.pid
兩者一樣執行後Product表:
1 | 蘋果 | 100 | 512 |
2 | 桔子 | 50 | 10 |