1.選擇列
1)select 列名1，列名2...
from 表名
select sno,sname
from student
2)所有列
select *
from 表名
3)計算列
select sno,grade+2 'newgrade'
from sc
select productid,price*stocks
from products
select rtrim()sname+'是'+rtrim(s***)+'生'
from student
擷取空格的函式
rtrim()
4)增加列標題
『列標題』=列名
列名 [as] 『列標題』
select '學號'=sno,sname as '姓名'
from student
2.選擇行
select...
from...
where...
1)比較運算子
>,<,<>,!=,...
select sno,grade
from sc
where grade>80
select *
from student
where s***='男'
select *
from student
where year(sbrithday)=1991
select *
from student
where year(getdate())-year(sbrithday)>20
select year(sbrithday),sname
from student
2)邏輯運算子
not,and,or
not>and>or
select *
from sc
where cno='c101' and grade>80
select*
from sc
where cno='c101' and(grade>80 or grade<60)
select*
from sc
where cno='c102' and (grade<60 or grade is null)
補充:null 不確定
is null 比較某一列是否為空
3.查詢範圍
間斷in(...) x in(a,b)===x=a or x=b
not in(a,b)===x!=a and x!=b
連續between..and... x between a and b ====
select*
from sc
where grade between 80 and 100
select *
from sc
where cno in('c101','c103','c105')
select productname,productid
from products
where price*stocks between 50 and 1000
select *
from products
where price>50 or stocks<100
select *
from products
where price is null
4.模糊查詢 like
% _ [^](四個佔位符)
select *
from student
where sname like '李%'
select *
from student
where sname like '%偉%'
select *
from student
where sname like '_偉%'
select*
from student
where sname like '%偉'
select *
from student
where sname not like'%偉%'
select *
from student
where sname not like '_偉%'
或者select *
from student
where sname like '_[^偉]%'
select *
from student
where rtrim(sname) like '李_'
select *
from student
where rtrim(sname) like '[李、張]_ '
5.
1).消除重複值 distinct
select distinct cno
from sc
where grade<60 or grade is null
2).top n,top n percent
select top 3*
from student
select top 10 percent *
from student
3).order by 列名 asc(公升序)|desc(降序),(如果沒寫的情況下預設為asc)
select *
from sc
order by grade desc
select top 3 *
from sc
where cno='c101'
order by grade desc
練習
1查詢products表中總價量最高的5種產品名字
2查詢products表中單價在20~40之間的產品資訊
3查詢products表中三個字的產品有哪些
select top 5 productname
from products
order by price*stocks desc
select*
from products
where price between 20 and 40
select *
from products
where rtrim (productname) like '___'
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