如需命名 CHECK 约束,并定义多个列的 CHECK 约束,请使用下面的 SQL 语法: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons ADD CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes') 撤销CHECK 约束 如需撤销 CHECK 约束,请使用下面的 SQL: SQL Server / Oracle / MS Access: ALTE...
CHECK Constraint in Existing Table We can add theCHECKconstraint to an existing table by using theALTER TABLEclause. For example, let's add theCHECKconstraint to theamountcolumn of an existingOrderstable. -- add CHECK constraint without nameALTERTABLEOrdersADDCHECK(amount >0); Here's how we c...
可以使用 SQL Server Management Studio 或 Transact-SQL 在表中创建检查约束,以指定 SQL Server 的一个或多个列中可接受的数据值。 要详细了解如何添加列约束,请参阅 ALTER TABLE column_constraint。 有关详细信息,请参阅 Unique 约束和 check 约束。 备注 若要查询现有的检查约束,请使用 sys.check_constraints...
可以使用 SQL Server Management Studio 或 Transact-SQL 在表中创建检查约束,以指定 SQL Server 的一个或多个列中可接受的数据值。 要详细了解如何添加列约束,请参阅ALTER TABLE column_constraint。 有关详细信息,请参阅Unique 约束和 check 约束。
IF OBJECT_ID ('dbo.Vendors', 'U') IS NOT NULL DROP TABLE dbo.Vendors; GO CREATE TABLE dbo.Vendors (VendorID int PRIMARY KEY, VendorName nvarchar (50), CreditRating tinyint) GO ALTER TABLE dbo.Vendors ADD CONSTRAINT CK_Vendor_CreditRating CHECK (CreditRating >= 1 AND CreditRating <= ...
CONSTRAINT check_constraint_nameCHECK(expression);Code language:SQL (Structured Query Language)(sql) When a check constraint is on the same line as the table column, its syntax is called in-line constraint. Alternatively, you can can define a check constraint using a table constraint syntax: ...
So the constraint won’t be enforced and we can insert data into the table t2 that doesn’t match the data in t1, but we don’t want to do this, so we can enable the constraint again using this SQL: 1 alter table t2 CHECK CONSTRAINT fk_t2_t1 ...
Drop constraint in Oracle: We can drop the constraint in Oracle using the alter table command. we can drop primary, foreign key, check, not null and unique constraint with the same command Coalesce Function in Oracle: The Coalesce function in Oracle will return the first expression if it is...
in a loss of precision, an error occurs. Note Constraint expression evaluation the SQL mode in effect at evaluation time. If any component of the expressiondepends on the SQL mode, different results may occur for different uses of the table unless the SQL mode is the same during all...
SQL> select distinct status from v$archived_log; S - A D Now the workaround is to recreate the standby controlfile (which is proven to be good because of the query earlier). That’s a fairly straight forward operation since the database is using a file system. A simple “ALTER DATABAS...