SQL Server Implementation Change table name, change column name, change constraint code

1. Modify the table name

Format: sp_rename tablename,newtablename

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1	sp_rename tablename,newtablename

2. Modify the field name

Format: sp_rename ' Tablename.colname ', Newcolname, ' column '

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1	sp_rename ‘tablename.colname‘,newcolname,‘column‘

3. Add a Field

Format: ALTER TABLE table_name add New_column data_type [interality_codition]

Example 1

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1	ALTERTABLE student Addnationality varchar(20)

--Example 2 adds a column of type int, the default value is 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‘) beginalter table student DROP COLUMN nameend

4. Changing fields

Format: ALTER TABLE table_name ALTER COLUMN COLUMN_NAME

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1	ALTERTABLE student ALTER COLUMN nameVARCHAR(200)

5. Delete a field

Format: ALTER TABLE table_name DROP COLUMN column_name

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1	ALTERTABLE student DROP COLUMNnationality;

6. View field constraints

Format: SELECT * FROM information_schema.constraint_column_usage WHERE table_name = table_name

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12	SELECTTABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME FROM information_schema.CONSTRAINT_COLUMN_USAGEWHERETABLE_NAME = ‘student‘

7. View field Default constraint expressions (that is, default values, etc.)

Format: SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = table_name

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12	SELECTTABLE_NAME, COLUMN_NAME, COLUMN_DEFAULT FROM information_schema.COLUMNSWHERETABLE_NAME=‘student‘

8. View the field DEFAULT constraint name

Format: select name from sysobjects where OBJECT_ID (table_name) =parent_obj and xtype= ' D '

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12	selectname from sysobjectswhere object_id(‘表?名?‘)=parent_obj andxtype=‘D‘

9. Delete field constraints

Format: ALTER TABLE tablename DROP constraint ConstraintName

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1	ALTERTABLE student DROP CONSTRAINTPK__student__2F36BC5B772B9A0B

10. Adding field constraints

Format: ALTER TABLE tablename ADD constraint ConstraintName primary key (column_name)

--Example 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 stuInfoDrop Constraint PK_stuNoGo -- 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 stuInfoDrop Constraint UQ_stuIDGo -- 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_stuAddressGo -- 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

SQL Server Implementation Change table name, change column name, change constraint code