Some SQL statements often used in work and study

[Introduction] Some commonly used SQL statements: Create a new table:

 CREATE table [表名] ( [自动编号字段] int IDENTITY (1,1) PRIMARY KEY , [字段1] nVarChar(50) default 默认值 null , [字段2] ntext null , [字段3] d

Some commonly used SQL statements:

Create a new table:

create table [表名]
(
[自动编号字段] int IDENTITY (1,1) PRIMARY KEY ,
[字段1] nVarChar(50) default '默认值' null ,
[字段2] ntext null ,
[字段3] datetime,
[字段4] money null ,
[字段5] int default 0,
[字段6] Decimal (12,4) default 0,
[字段7] image null ,
)

Create a new table:

create table [表名]
(
[自动编号字段] int IDENTITY (1,1) PRIMARY KEY ,
[字段1] nVarChar(50) default '默认值' null ,
[字段2] ntext null ,
[字段3] datetime,
[字段4] money null ,
[字段5] int default 0,
[字段6] Decimal (12,4) default 0,
[字段7] image null ,
)

Delete table:

Drop table [table name]

Insert data:

INSERT INTO [表名] (字段1,字段2) VALUES (100,'51WINDOWS.NET')

Delete data:

DELETE FROM [表名] WHERE [字段名]>100

Update data:

UPDATE [表名] SET [字段1] = 200,[字段2] = '51WINDOWS.NET' WHERE [字段三] = 'HAIWA'

New field:

ALTER TABLE [表名] ADD [字段名] NVARCHAR (50) NULL

Delete field:

ALTER TABLE [表名] DROP COLUMN [字段名]

Modify field:

ALTER TABLE [表名] ALTER COLUMN [字段名] NVARCHAR (50) NULL

Rename table: (Access renames the table, please refer to the article: Rename the table in the Access database)

sp_rename 'Table name', 'New table name', 'OBJECT '

New constraint:

ALTER TABLE [表名] ADD CONSTRAINT 约束名 CHECK ([约束字段] <= &#39;2000-1-1&#39;)

Delete constraint:

ALTER TABLE [表名] DROP CONSTRAINT 约束名

New default Value

ALTER TABLE [表名] ADD CONSTRAINT 默认值名 DEFAULT '51WINDOWS.NET' FOR [字段名]

Delete default value

ALTER TABLE [表名] DROP CONSTRAINT 默认值名

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