Remove CHECK Constraint We can remove theCHECKconstraint using theDROPclause. For example, SQL Server, PostgreSQL, Oracle -- remove CHECK constraint named amountCKALTERTABLEOrdersDROPCONSTRAINTamountCK; MySQL -- remove CHECK constraint named amountCKALTERTABLEOrdersDROPCHECKamountCK; Also Read:...
CHECK constraints determine the valid values from a logical expression that is not based on data in another column. For example, it is possible to limit the range of values for a salary column by creating a CHECK constraint that allows only data that ranges from 15,000 through 500, 00. Th...
适用对象:SQL ServerAzure SQL 数据库Azure SQL 托管实例Microsoft Fabric 中的 SQL 数据库 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...
SQL Server / Oracle / MS Access: CREATETABLEPersons ( ID intNOTNULL, LastName varchar(255)NOTNULL, FirstName varchar(255), Age intCHECK(Age>=18) ); To allow naming of aCHECKconstraint, and for defining aCHECKconstraint on multiple columns, use the following SQL syntax: ...
Once defined, the database will only insert a new row or update an existing row if the new value satisfies the CHECK constraint. The CHECK constraint is used to ensure data quality. For example, in the following CREATE TABLE statement, ...
ADD CONSTRAINT check_supplier_name CHECK (supplier_name IN ('IBM', 'Microsoft', 'NVIDIA')); In this example, we've created a check constraint on the existing suppliers table called check_supplier_name. It ensures that the supplier_name field only contains the following values: IBM, Microsoft...
CREATE TABLE CheckTbl (col1 int, col2 int); GO CREATE FUNCTION CheckFnctn() RETURNS int AS BEGIN DECLARE @retval int SELECT @retval = COUNT(*) FROM CheckTbl RETURN @retval END; GO ALTER TABLE CheckTbl ADD CONSTRAINT chkRowCount CHECK (dbo.CheckFnctn() >= 1 ); GO 添加的 CHECK 约...
SQL Check Constraint - Learn how to use SQL Check Constraints to enforce data integrity in your database. Understand the syntax and examples for effective application.
A CHECK constraint on a column in a database table specifies that the values in the column must meet certain conditions.
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。