SQLSERVER实现更改表名，更改列名，更改约束代码

废话不多说了，具体详情如下所示：

1.修改表名

格式：sp_rename tablename,newtablename

sp_rename tablename,newtablename 

2.修改字段名

格式：sp_rename 'tablename.colname',newcolname,'column'

sp_rename 'tablename.colname',newcolname,'column' 

3.添加字段

格式：alter table table_name add new_column data_type [interality_codition]

示例1

alter table student add nationality varchar(20)

--示例2 添加int类型的列,默认值为 0

alter table student add studentname int default 0 --示例3 添加int类型的列,默认值为0，主键 
alter table student add studentid int primary key default 0 --示例4 判断student中是否存在name字段且删除字段 
if exists(select * from syscolumns where id=object_id('student') and name='name') begin 
alter table student drop column name 
end 

4.更改字段

格式：alter table table_name alter column column_name

alter table student alter column name varchar(200) 

5.删除字段

格式：alter table table_name drop column column_name

alter table student drop column nationality; 

6.查看字段约束

格式： select * from information_schema.constraint_column_usage where table_name = table_name

select table_name,column_name,constraint_name from information_schema.constraint_column_usage
where table_name = 'student' 

7.查看字段缺省约束表达式 （即默认值等）

格式：select * from information_schema.columns where table_name = table_name

select table_name, column_name, column_default from information_schema.columns
where table_name='student' 

8.查看字段缺省约束名

格式：select name from sysobjects where object_id(table_name)=parent_obj and xtype='d'

select name from sysobjects
where object_id('表?名?')=parent_obj and xtype='d' 

9.删除字段约束

格式：alter table tablename drop constraint constraintname

alter table student drop constraint pk__student__2f36bc5b772b9a0b 

10.添加字段约束

格式：alter table tablename add constraint constraintname primary key (column_name)

--示例1

alter table stuinfo add constraint pk_stuno primary key (stuno) --示例2 添加主键约束（primary key）


-- 存在主键约束pk_stuno，则删除 
if exists(select * from sysobjects where name='pk_stuno' and xtype='pk')
alter table stuinfo
drop constraint pk_stuno
go -- 重新添加主键约束pk_stuno 
alter table stuinfo add constraint pk_stuno primary key (stuno)
go --示例3 添加 唯一uq约束（unique constraint）
-- 存在唯一约束uq_stuno，则删除 
if exists(select * from sysobjects where name='uq_stuid' and xtype='uq')
alter table stuinfo
drop constraint uq_stuid
go 
-- 重新添加唯一约束uq_stuid 
alter table stuinfo add constraint uq_stuid unique (stuid) --示例4 添加默认df约束（default constraint）
-- 存在默认约束uq_stuno，则删除 
if exists(select * from sysobjects where name='df_stuaddress' and xtype='d')
alter table stuinfo drop constraint df_stuaddress
go -- 重新添加默认约束df_stuaddress 
alter table stuinfo add constraint df_stuaddress default ('地址不详') for stuaddress --示例5 检查ck约束（check constraint）
-- 存在检查约束uq_stuno，则删除 
if exists(select * from sysobjects where name='ck_stuage' and xtype='c')
alter table stuinfo drop cons

以上所述是小编给大家介绍的sqlserver实现更改表名，更改列名，更改约束代码，希望对大家有所帮助！