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2.4匯總查詢(xún)Group Query
//匯總查詢(xún)相當于會(huì )計報表中的小計匯總的功能

語(yǔ)法: select ...
from <tablename>
group by <column-name >
[having search expression]

代碼:
//求出每名銷(xiāo)售人員的銷(xiāo)售金額
select rep,sum(amount) from orders group by rep
//每個(gè)銷(xiāo)售點(diǎn)分配了多少銷(xiāo)售人員
select rep_office,count(*) from salesreps group by rep_office
//計算每名銷(xiāo)售人員的每個(gè)客戶(hù)和訂單金額
select cust,rep,sum(amount) from orders group by cust,rep
//Having子句應用
select rep,avg(amount) from orders having sum(quota) > 3000.00

/**********************************************************/
3.數據修改DATA MODIFY LANGUAGE
3.1插入數據Insert
3.2修改數據Update
3.3刪除數據Delete
-----------------------------------------------------------
3.1插入數據Insert
3.1.1.單行插入
語(yǔ)法:insert into <tablename>[<columnlist,>...] values(<valuelist,>...);

代碼:
//不省略字段清單
insert into salesreps(name,age,empl_no,sales,title,hire_date,rep_office)
values('jack toms',36,111,0.00,'sales mgr','10-05-2010',13)
//省略字段清單
insert into salesreps
values('jack toms',36,111,0.00,'sales mgr','10-05-2010',13)
3.1.2.多行插入
語(yǔ)法:insert into <tablename>[(<columnlist,>...)] values(<valuelist,>...) <select Query>;

代碼:
//把一批數據批量插入到一個(gè)備份表中
insert into history_order(order_num,order_date,amount)
select order_num,order_date,amount
from orders where order_date < '01/01/2000'
-----------------------------------------------------------
3.2修改數據Update
語(yǔ)法:update <tablename> set (cloumn=expression...) [where ...] [SubQuery..]

代碼:
//更新所有記錄
update salesreps set quota=1.05 * quota
//按條件更新表記錄
update salesreps set quota=1.08 * quota where area='china'
//按子查詢(xún)更新表記錄
update customers set cust_rep=105
where cust_rep in (
selct empl_num from salesreps where sales < (0.8 * quota)
)

-----------------------------------------------------------
3.3刪除數據Delete
語(yǔ)法1:delete from <tablename> [where ...]
代碼:
//所有刪除記錄
delete from orders

語(yǔ)法2:truncate table <tablename>
代碼2:
//所有刪除記錄
truncate table orders

//按條件刪除記錄
delete from orders where order_date < '01/01/2000'