时间：2021-07-01 10:21:17 帮助过：15人阅读
1.修改表名
格式：sp_rename tablename,newtablename
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sp_rename tablename,newtablename
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2.修改字段名
格式：sp_rename ‘tablename.colname‘,newcolname,‘column‘
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sp_rename ‘tablename.colname‘,newcolname,‘column‘
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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)
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--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
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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)
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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;
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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‘
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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‘
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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‘
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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
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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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SQLSERVER实现更改表名，更改列名，更改约束代码
标签：containe end address var tool 约束 number com alt