IFNOTEXISTS(SELECT*FROMINFORMATION_SCHEMA.COLUMNS WHERETABLE_NAME='LandlordInfo'ANDCOLUMN_NAME='IsSigned') BEGIN ALTERTABLELandlordInfoADDIsSignedbitnull END
HOST_NAME() ---函数返回服务器端计算机的名称 IDENTITY([, seed increment]) [AS column_name]) --IDENTITY() 函数只在SELECT INTO 语句中使用用于插入一个identity column列到新表中 /**//**//**//*select identity(int, 1, 1) as column_name into newtable from oldtable*/ ISDATE() ---函数...
alter table t alter column c2 nvarchar(200) 範例程式碼 4-34:更動既有資料表的資料行類型時,小心是否導致大量 I/O 01 02 03 4-2 05 06 07 資料類型 14 這一點有人在大聲疾呼,一定要讓其變成可讀寫,你可以參考如下的網址: https://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?Feed...
Where exists(select * from课程注册 where学号=学生。学号and课程号='1') 五、约束 1、创建主键约束: Alter table table_name Add constraint pk_name Primary key ( column_name ) 2、创建UNIQUE约束: Alter table table_name Add constraint uk_name Unique ( column_name ) 3、创建CHECK约束: Alter table...
owner.table_name add column_name char(2) null .. sp_help table_name--- 显示表已有特征 create table tablename (name char(20), age smallint, lname varchar(30)) insert into tablename select --- 实现删除列的方法(创建新表) alter table tablename drop constraint Stockname_default --...
Alter Table Add Column if Not Exists to update Schema Modification Script Alter Table add Column - How do you add a column after say the second column Alter table add constraint primary key clustered identity(1,1) ALTER TABLE ALTER COLUMN (To set the default value) ALTER TABLE Progress? ALT...
drop column u_id; --3. 添加字段 alter table uinfor add u_note varchar(1) NULL; --4. 修改字段 --if exists(select * from syscolumns where id=object_id(N'uinfor') and name='u_key') alter table uinfor alter column u_key varchar(18) NOT NULL; ...
if not exists ( select column_name from INFORMATION_SCHEMA.columns where table_name = 'table_name' and column_name = 'new_column_name' ) ALTER TABLE table_name add new_column_name TEXT Option 2: Check the column existance 1 2 3
altercolumn列名修改表列属性 add(列定义,计算列定义,表约束定义) dropcolumn列名删除列 三、数据的基本操作 1、数据的添加 Insertintotable_name(column1,column2,column3,…) Values(‘expression1’,’expression2’,’expression3’,…) 2、数据的修改 ...
[ , ] ...n ] ] ) |FORTIMESTAMPASOF'<point_in_time>'}::={NOEXPAND[ ,INDEX(<index_value>[ , ...n ] ) |INDEX= (<index_value>) ] |INDEX(<index_value>[ , ...n ] ) |INDEX= (<index_value>) |FORCESEEK[ (<index_value>(<index_column_name>[ , ... ] ) ) ] |FORCESC...