ROBINSON SYS_C005554 U TB_CONSTRAINT_3 ENABLEDNOTDEFERRABLE VALIDATED--两列上具有相同的约束名SQL>SELECT*FROMuser_cons_columnsWHEREtable_name='TB_CONSTRAINT_3'; OWNER CONSTRAINT_NAME TABLE_NAME COLUMN_NAME POSITION--- --- --- --- ---ROBINSON SYS_C005554 TB_CONSTRAINT_3 EMAIL1ROBINSON PK_T...
按照上面创建Check约束的方法,已经Alter Table时,表中本身已经存在不符合的数据,那么Alter Table操作将被SQL Server拒绝执行。除非已经存在的所有数据都满足CHECK约束的条件,否则SQL Server不会执行创建约束的命令。要解决这个问题,我们可以添加WITH NOCHECK。 我们先新建一个表只有3个字段的表,Id、姓名、年龄,并在里面...
--下面是在SQL server 2005中的演示,不存在上述出现的问题 --理论上空字符串('')并不等于NULL,不知道为什么在Oracle 10g中出现了错误提示 CREATE TABLE tb_constraint_1 ( empno int PRIMARY KEY, --主键约束 ename VARCHAR(20) NOT NULL, --非空约束 email VARCHAR(60) UNIQUE, --唯一约束 sal int CHEC...
Starting in SQL Server 2012 this may be a meta data operation adding-not-null-columns-as-an-online-operation. If this is used when the related column isn't also being added then it has no effect. CHECK Is a constraint that enforces domain integrity by limiting the possible values that ...
In this article Syntax Arguments Remarks Examples See Also Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Specifies the properties of a PRIMARY KEY, FOREIGN KEY, UNIQUE, or CHECK constraint that is part of a new column definition added to a table by using ALTER ...
the column's value will always be set to the value given in the DEFAULTconstant expression. Starting in SQL Server 2012 this may be a meta data operationadding-not-null-columns-as-an-online-operation. If this is used when the related column isn't also being added then it has no effect...
Specifies what action happens to rows in the table that is altered, if those rows have a referential relationship and the referenced row is deleted from the parent table. The default is NO ACTION. NO ACTION The SQL Server Database Engine raises an error and the delete action on the row in...
SQL Server: ALTERTABLEPersons ADDCONSTRAINTdf_City DEFAULT'Sandnes'FOR City; MS Access: ALTERTABLEPersons ALTERCOLUMNCitySETDEFAULT'Sandnes'; Oracle: ALTERTABLEPersons MODIFYCityDEFAULT'Sandnes'; DROP a DEFAULT Constraint To drop aDEFAULTconstraint, use the following SQL: ...
To drop aUNIQUEconstraint, use the following SQL: MySQL: ALTERTABLEPersons DROPINDEXUC_Person; SQL Server / Oracle / MS Access: ALTERTABLEPersons DROPCONSTRAINTUC_Person; ❮ PreviousNext ❯ Track your progress - it's free! Log inSign Up...
(Inherited from TSqlFragment) Properties 展開資料表 ConstraintIdentifier The name of the constraint. FirstTokenIndex Gets or sets the first index of the token. (Inherited from TSqlFragment) FragmentLength Defines the number of characters the fragment takes up in the s...