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SQL語句的基本操作

 

--創建數據庫
create database Etp;


--連接數據庫
connect to Etp;


--斷開連接
disconnect Etp;


--查看當前數據庫下有哪些表
list tables;


--建表
create table studentInfo(
 stuno char(5) not null,
 stuname varchar(8),
 stubirth date
);


--查看表結構
describe table studentinfo;


--新增表字段
alter table studentinfo add stutel int;
alter table studentinfo add abc int;


--修改字段類型
alter table studentinfo alter column stutel set data type char(11);


--刪除字段
alter table studentinfo drop column abc;


--增加一個非空約束
alter table studentinfo alter column stuname set not null;

 

--重構表
reorg table studentinfo;

 

--增加一個唯一約束
alter table studentinfo alter column stutel set not null;
alter table studentinfo add constraint un_stutel unique(stutel);

 

--添加檢查約束
alter table studentinfo add column stuAge int;
alter table studentinfo add constraint ch_stuAge check(stuAge > 0 and stuAge <150);

 

--添加主鍵約束
alter table studentinfo add constraint pk_stuno primary key(stuno);

 

--刪除表
drop table studentinfo;

 

--創建表的同時添加約束方式1
create table studentinfo(
 stuNo int not null,
 stuName varchar(8) not null,
 stuAge int,
 stuTel char(8),
 constraint pk_stuNo primary key(stuNo),
 constraint un_stuName unique(stuName),
 constraint ch_stuAge check(stuAge >=0 and stuAge <150)
);

 

--創建表的同時添加約束方式2
create table studentinfo(
 stuNo int not null primary key,
 stuName varchar(8) not null unique,
 stuAge int check(stuAge >=0 and stuAge <150),
 stuTel char(8)
);

 

--添加主外鍵
--新增班級表
create table classInfo(
 classId int not null primary key,
 className varchar(20)
);

 


--建表的同時添加外鍵
create table studentinfo(
 stuNo int not null,
 stuName varchar(8) not null,
 stuBirth date not null,
 stuAge int,
 stuTel char(8),
 fclassId int,
 stuBirth date not null,
 constraint pk_stuNo primary key(stuNo),
 constraint un_stuName unique(stuName),
 constraint ch_stuAge check(stuAge >=0 and stuAge <150),
 constraint fk_fcalssId foreign key(fclassid) references classInfo(classId)
);


-- 自增
create table studentinfo(
 stuNo int not null generated always as identity(start with 1 ,increment by 1),
 stuName varchar(8) not null,
 stuAge int,
 stuTel char(8),
 fclassId int,
 stuBirth date not null,
 constraint pk_stuNo primary key(stuNo),
 constraint un_stuName unique(stuName),
 constraint ch_stuAge check(stuAge >=0 and stuAge <150),
 constraint fk_fcalssId foreign key(fclassid) references classInfo(classId)
);


--先建表再添加外鍵
alter table studentinfo add constraint fk_classId foreign key(fclassid) references classInfo(classId);


--從係統表中查詢約束名
select constname, tabname, refkeyname, reftabname, colcount, deleterule, updaterule from syscat.references;


--插入
insert into classinfo values(1,'ETP-1');
insert into studentInfo values(1,'xy,20,'12345',1,'1995-01-21');

--不是全部插入則需要寫列名
insert into studentinfo(stuNo,stuName,stuTel) values(2,'wj','111');

                  
-- 有自增長的列要寫清楚列名
insert into studentinfo(stuName,stuAge,stuTel,fclassid,stuBirth) values('xy,20,'12345',1,'1995-01-21');
insert into studentinfo(stuName,stuAge,stuTel,fclassid,stuBirth) values('tom',22,'12345',2,'1995-01-21');


--更新
update studentinfo set stuBirth = '1990-02-21' where stuName='xy';
update studentinfo set stuBirth = '1990-02-21',stuAge = 21 where stuName='xy';


--刪除
deleted from studentinfo where stuName='xy';


--查詢
select * from studentinfo where stuName='xy';
select stuName,stuAge from studentinfo;


--別名查詢
select stuName as 姓名,stuAge as 年齡 from studentinfo;
select s.stuName as 姓名,s.stuAge as 年齡 from studentinfo s;


--運算查詢
select s.stuName as 姓名,s.stuAge+5 as 年齡 from studentinfo s;


--串聯運算查詢
select stuName||stuAge from studentinfo;


--and 和 or
select s.stuName as 姓名,s.stuAge+5 as 年齡 from studentinfo s where s.stuName='xy' and s.stuAge=20;
select s.stuName as 姓名,s.stuAge+5 as 年齡 from studentinfo s where s.stuName='xy' or s.stuAge=20;


--null
select * from studentinfo where stuAge is null; 
select * from studentinfo where stuAge is not null; 

 

--between and 包括邊界 相當於>=和<=s
select s.stuName as 姓名,s.stuAge+5 as 年齡 from studentinfo s where s.stuAge between 10 and 20


--in
select * from studentinfo  where stuName in ('xy','wj');
select * from studentinfo  where stuName not in ('xy','wj');


--模煳查詢 like%,%表示多個字符
select * from studentinfo where stuName like 'x%'

 

--模煳查詢 like_ , _表示單個字段
select * from studentinfo where stuName like 'x_';

 

--排序 order by
select * from studnetinfo order by fclassid desc;
select * from studnetinfo order by fclassid asc;


--distinct去掉重複
select distinct stuAge as 年齡 from studentinfo;


--group by,使用的時候,select 後麵隻能加2種字段: 1.group by 後麵出現的,2.聚合函數

select fclassId as 班級號,count(stuName) as 學生個數 from studentinfo group by fclassid;


-having 在分組的基礎上過濾,出現順序where-group by-having

select fclassId as 班級號,count(stuName) as 學生個數 from studentinfo group by fclassid having count(StuName)>=2

 

 

最後更新:2017-04-03 05:40:35

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