SQL语句简单例子-笔记

--------建表-------------

create table student(

_id integer primary key autoincrement ,

stu_no varchar(10) not null,

class_name varchar(20) not null,

stuname varchar(20) not null,

sex char(4) ,

age integer,

height real

);

---------查询表中的数据------------

select * from student;

------------删除表---------------------

drop table student;

--------往表中增加5条数据---------------

--------insert into 表名(列名) values (值)------------------------

insert into student(stu_no,class_name,stuname) values

('and02','android1412','张三');

insert into student(stu_no,class_name,stuname,sex,age,height)

values('and03','android1412','张三','男',21,178.5);

insert into student(stu_no,class_name,stuname,sex,age,height) values

('and04','android1412','张三','男',22,178.5);

insert into student(stu_no,class_name,stuname,sex) values

('and05','android1412','李四','男');

insert into student(stu_no,class_name,stuname,sex,age) values

('and06','android1412','徐士杰','男',23);

---------------将学号为3的学生的性别修改为女------------------------

update student set sex='女' where stu_no='and03';

-------------------将学号为2的学生的名字修改为"小李"---------

update student set stuname='小李' where stu_no='and02';

--------将高度为160cm以上的高度修改为162---------

update student set height=162 where height>160;

----将学号为3的学生年龄修改为21岁--------

update student set age=21 where stu_no='and03';

update student set age=20 where stuname='张三';

---将名字为张三并且年龄为20岁的男的年龄修改为23-----------

update student set age=23

where stuname='张三' and age=20 and sex='男';

------将名字里有一个'刘'的年龄设为22-------------

update student set stuname='刘三姐' where _id=2;

update student set age=22 where stuname like '%刘%';

--将名字只有2个字,并且最后一个字为四的高度设为170---

update student set height=170 where stuname like '_四';

------修改编号为1的性别，年龄，高度-------

update student set sex='女',age=18,height=162 where _id=1;

--将高度为162的年龄都增加2岁---

update student set age=age+2 where height=162;

--将班级为android1412班并且性别为女的高度统一设为160---

update student set height=160

where class_name='android1412' and sex='女';

--将班级为android1412的,或者性别为女的高度设为159----

update student set class_name='android1413',sex='女' where _id=4;

update student set height=159

where class_name='android1412' or sex='女';

---修改名字为张三或者李四的年龄为23-----

update student set age=23 where stuname='张三' or stuname='李四';

update student set age=20 where stuname in('张三','李四');

------删除id为5的学生信息--------

delete from student where _id=5;

-------查询所有记录--------------

select * from student;

---查询班级名称为and1412的学生记录-----

select * from student where class_name='android1412';

----查询班级名称为and1413的姓名和年龄------

select stuname,age from student where class_name='android1413';

----在查询结果中增加一列,列明为school,值为北大-------

select stuname,age,'北大' as school from student;

---查询年龄在20岁以及以上的学生记录----

select * from student where age>=20;

------查询学生为张三或者李四的记录----------

select * from student where stuname in('张三','李四');

---统计每个班的人数,按班级分组------

select class_name,count(*) from student group by class_name;

----统计每个班年龄大于22岁的总人数,按班级分组-------

select class_name,count(*) from student

where age>22

group by class_name;

------统计班级人数,年龄大于20,并且人数在3人以上的记录--------------

select class_name,count(*) from student

where age>20

group by class_name

having count(*)>3;

-----查询表中年龄最大的记录-------

select max(age) from student;

select * ,max(age) from student ;

-----查询表中年龄最小的记录------

select *,min(age) from student;

---查询1412班的平均年龄---

select class_name,avg(age) from student

where class_name='android1412';

--查询所有班级的平局年龄-----

select class_name,avg(age) from student

group by class_name;

---统计班上的人数的总年龄,将列名为总年龄---

select class_name,sum(age) as '总年龄' from student

group by class_name;

----将表中的记录按照年龄升序--order by 列名,desc 降序，asc:升序,默认---

select * from student order by age asc;

------将表中的记录按照年龄降序----

select * from student order by age desc;

---统计班级年龄大于20的人数,按降序排序---

select class_name,count(*) from student

where age>20

group by class_name

order by count(*) desc;

----统计班级年龄大于20的并且年龄大于20的总人数大于2的记录,按降序-------

-----先条件，再分组，再筛选，再排序---------

select class_name,count(*) from student

where age>20

group by class_name

having count(*)>2

order by count(*) desc;

---查询年龄最大的前3个记录----

select * from student

order by age desc

limit 0,3;

------------建表------------

create table student(

_id integer primary key not null,

stu_no varchar(10) not null,

class_name varchar(20) not null,

stuname varchar(20) not null,

sex char(4),

age integer,

height real

);

------------建表------------

create table newstud(

_id integer primary key autoincrement,

stu_no varchar(10) not null,

class_name varchar(20) not null,

stuname varchar(20) not null,

sex char(4),

age integer,

height real

);

-----------查询表中数据---------------

select * from student

select * from teacher

------------删除表-------------------

drop table student