sql语句
2015-09-29 11:29
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修改表名
格式:sp_rename tablename,newtablenamesp_rename tablename,newtablename
修改字段名
格式:sp_rename 'tablename.colname',newcolname,'column'sp_rename 'tablename.colname',newcolname,'column'
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
更改字段
格式:alter table table_name alter column column_nameALTER TABLE student ALTER COLUMN name VARCHAR(200)
删除字段
格式:alter table table_name drop column column_nameALTER TABLE student DROP COLUMN nationality;
查看字段约束
格式: select * from information_schema.constraint_column_usage where TABLE_NAME = table_nameSELECT TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME FROM information_schema.CONSTRAINT_COLUMN_USAGE WHERE TABLE_NAME = 'student'
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_nameSELECT TABLE_NAME, COLUMN_NAME, COLUMN_DEFAULT FROM information_schema.COLUMNS WHERE TABLE_NAME='student'
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'
删除字段约束
格式:alter table tablename drop constraint constraintnameALTER TABLE student DROP CONSTRAINT PK__student__2F36BC5B772B9A0B
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
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