軟件測試

Mysql-Sql查詢匯總

簡單查詢

創建students表

create table students(

id int not null unique primary key auto_increment,

name varchar(10) not null,

class varchar(10) not null,

grade int

)

添加數據

insert into students values(0,'老1','1班',80);

insert into students values(0,'老2','2班',90);

insert into students values(0,'老3','3班',86);

insert into students values(0,'老4','4班',70);

insert into students values(0,'老5','5班',89);

insert into students values(0,'老6','6班',93);

查詢所有數據

select * from students

查詢指定字段

select name,class from students

通過as給表起別名

select s.name,s.class from students as s

通過as給字段起別名

select name as 姓名,class as 班級 from students

條件查詢

比較運算

select * from students where class='1班'

select * from students where grade>90

邏輯運算

and、or、not

select * from students where grade<90 and class!='1班'

模糊查詢

like、%任意多個字符、_一個任意字符

select * from students where name like '老%'

select * from students where name like '%5'

范圍查詢

in表示非連續范圍內、between...and...在一個連續范圍內

select * from students where class in('1班','3班','4班')

select * from students where grade between 80 and 90

空判斷

is null 與' '不同，' '為空字符串

select * from students where grade is null

select * from students where class=' '

insert into students(name,class,grade) values('老7','1班',null)

排序

order by 列1 asc|desc,列2 asc|desc

asc從小到大，升序，不寫則為升序

desc從大到小，降序

select * from students order by grade

先按grade降序、再按id升序

select * from students order by grade desc,id

先按id升序、再按grade降序

select * from students order by id,grade desc

聚合函數

count

select count(*) from students

帶字段的不統計為null的數據

select count(grade) from students

max、min、sum、avg

select max(grade) from students

select avg(grade) from students

分組

select sex,count(*) from students group by sex

select grade,count(*) from students group by grade

select class,grade,count(*) from students group by grade,class

分組后過濾

使用having，必須跟在group by之后

where是用于from后的數據篩選、having是對group by的結果進行篩選

獲取部分行

索引0開始

select * from students order by grade limit 0,3

分頁

每頁顯示m條數據，第n頁的數據

select * from students limit (n-1)*m,m

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