SQLSERVER实现更改表名,更改列名,更改约束代码
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1.修改表名
格式:sp_rename tablename,newtablename
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sp_rename tablename,newtablename |
2.修改字段名
格式:sp_rename ‘tablename.colname‘,newcolname,‘column‘
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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
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ALTER TABLE student Add nationality varchar (20) |
--示例2 添加int类型的列,默认值为 0
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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
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ALTER TABLE student ALTER COLUMN name VARCHAR (200) |
5.删除字段
格式:alter table table_name drop column column_name
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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
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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
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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‘
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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
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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
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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 |
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