SQL Server 数据库基础语法、数据类型

--Go批处理语句用于将go之前的语句合并为为一个语句块,同时执行多个语句

--使用、切换数据库

usemaster

go

--创建、删除数据库

--示例1

if(exists(select*fromsys.databaseswherename='testHome'))

dropdatabasetestHome

go

createdatabasetestHomeon

(

name='testHome',

filename='c:\data\students.mdf'

)

logon

(

name='testHome_log',

filename='c:\data\testHome_log.ldf'

)

go

--示例2

if(exists(select*fromsys.databaseswherename='testHome'))

dropdatabasetestHome

go

createdatabasetestHomeonprimary//默认就是primary,onprimary是可省略的

(

name='testHome_data',

fileName='c:\testHome_data.mdf',

size=3MB,

maxSize=50MB,

fileGrowth=10%

)

logon

(

name='testHome_log',

fileName='c:\testHome_log.ldf',

size=1MB,

fileGrowth=1MB

)

go

--判断某个表或对象是否存在

if(exists(select*fromsys.objectswherename='classes'))

print'存在';

go

if(exists(select*fromsys.objectswhereobject_id=object_id('student')))

print'存在';

go

if(object_id('student','U')isnotnull)

print'存在';

go

--判断该列名是否存在，如果存在就删除(删除列需要确保这个列中没有数据)

if(exists(select*fromsys.columnswhereobject_id=object_id('student')andname='idCard'))

altertablestudentdropcolumnidCard

go

if(exists(select*frominformation_schema.columnswheretable_name='student'andcolumn_name='tel'))

altertablestudentdropcolumntel

go

--判断是否存在当前table

if(exists(select*fromsys.objectswherename='classes'))

droptableclasses

go

createtableclasses(

idintprimarykeyidentity(1,2),

namevarchar(22)notnull,

createDatedatetimedefaultgetDate()

)

go

if(exists(select*fromsys.objectswhereobject_id=object_id('student')))

droptablestudent

go

--创建table

createtablestudent(

idintidentity(1,1)notnull,

namevarchar(20),

ageint,

sexbit,

cidint

)

go

--添加字段

altertablestudentaddaddressvarchar(50)notnull;

--修改字段

altertablestudentaltercolumnaddressvarchar(20);

--删除字段

altertablestudentdropcolumnnumber;

--添加多个字段

altertablestudent

addaddressvarchar(22),

telvarchar(11),

idCardvarchar(3);

--添加新列、约束

altertablestudentaddnumbervarchar(20)nullconstraintno_ukunique;

--增加主键

altertablestudentaddconstraintpk_idprimarykey(id);

--添加外键约束

altertablestudentaddconstraintfk_cidforeignkey(cid)referencesclasses(id);

--添加唯一约束

altertablestudentaddconstraintname_ukunique(name);

--添加check约束

altertablestudentwithnocheckaddconstraintcheck_agecheck(age>1);

altertablestudentaddconstraintck_agecheck(age>=15andage<=50);

--添加默认约束

altertablestudentaddconstraintsex_defdefault1forsex;

--添加一个包含默认值可以为空的列

altertablestudentaddcreateDatesmalldatetimenull

constraintcreateDate_defdefaultgetDate()withvalues;

--多个列、约束一起创建

altertablestudentadd

/*添加id主键、自增*/

idintidentityconstraintidprimarykey,

/*添加外键约束*/

numberintnullconstraintuNumberreferencesclasses(number),

/*默认约束*/

createDatedecimal(3,3)constraintcreateDatedefault2010-6-1

go

--删除约束

altertablestudentdropconstraintno_uk;

--多条记录同时插入

insertintostudent

select'jack',23,1,5union

select'tom',24,0,3union

select'wendy',25,1,3union

select'tony',26,0,5;

--备份、复制student表到stu

select*intostufromstudent;

select*intostu1from(select*fromstu)t;

--查询student相关信息

execsp_helpstudent;

execsp_helpclasses;