drop table 表名 表的清单存放在该库的系统表sysobjects中 demo: usetext_datagoifexists(select*fromsysobjectswherename='textinfo')--检测textinfo表是否存在droptabletextinfo--删除表textinfocreatetabletextinfo--创建表textinfo( Tidintidentity(1,1)primarykeynotnull,--主键、标识列订、不可为空Tinfonvarchar(200...
DROPTABLEpeoInfo 三、使用SQL语句创建和删除约束 约束的目的是确保表中数据的完整性。 常用的约束类型: 主键约束(Primary Key constraint):要求主键列数据唯一,并且不允许为空。 唯一约束(Unique Constraint):要求该列唯一,允许为空,但只能出现一个空值。 检查约束(Check Constraint):某列取值范围显示、格式限制等,...
drop constraint PK_uinfor; -- 方法二(删除原主键) if exists(select * from sysobjects where xtype='PK' and parent_obj=object_id(N'uinfor') ) begin --使用动态语句可以保证无论主键名是怎么定义都可以正常删除 declare @s nvarchar(4000) select @s=N'alter table uinfor drop constraint'+quotenam...
DROP TABLE IF EXISTS dbo.Emp; GO CREATE TABLE dbo.emp ( empid INT NOT NULL CONSTRAINT PK_emp_empid PRIMARY KEY, mgrid INT NULL CONSTRAINT FK_emp_empid REFERENCES dbo.emp, empname VARCHAR(25) NOT NULL, jobtitle VARCHAR(25) NOT NULL, salary int NOT NULL, CHECK (empid <> mgrid) ); ...
DROP TABLE IF EXISTS dbo.Emp; GO CREATE TABLE dbo.emp ( empid INT NOT NULL CONSTRAINT PK_emp_empid PRIMARY KEY, mgrid INT NULL CONSTRAINT FK_emp_empid REFERENCES dbo.emp, empname VARCHAR(25) NOT NULL, jobtitle VARCHAR(25) NOT NULL, salary int NOT NULL, CHECK (empid <> mgrid) ); ...
DROP 或者 VALUES DUMP ORDER VARYING ELSE OUTER VIEW END OVER WAITFOR ERRLVL PERCENT WHEN ESCAPE PIVOT WHERE EXCEPT PLAN WHILE EXEC PRECISION WITH 執行CREATE 陳述式之前,請先執行 PRIMARY WITHIN GROUP EXISTS PRINT WRITETEXT EXIT PROC 下表列出 Azure Synapse Analytics 專屬的保留關鍵...
constraint violation occurs.SETXACT_ABORTON;BEGINTRYBEGINTRANSACTION;-- A FOREIGN KEY constraint exists on this table. This-- statement will generate a constraint violation error.DELETEFROMProduction.ProductWHEREProductID =980;-- If the DELETE statement succeeds, commit the transaction.COMMITTRANSACTION;...
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...
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...
If the value violates the primary key constraint and you use the identity column sequence value again, the following error might be raised: SQL Error [23505]: ERROR: duplicate key value violates unique constraint "emps_iden_pkey" Detail: Key (emp_id)=(2) alread...