SQL Server / Oracle / MS Access: ALTERTABLEPersons ALTERCOLUMNCityDROPDEFAULT; Exercise? What is the primary purpose of the SQLDEFAULTconstraint? To ensure all values in a column are unique To set a default value for a column when no value is specified ...
将上述步骤整合在一起,你可以得到以下 SQL 代码: -- 创建一个名为 Employees 的表CREATETABLEEmployees(EmployeeIDINTPRIMARYKEY,FirstName NVARCHAR(50),LastName NVARCHAR(50),JoiningDateDATE);-- 为 JoiningDate 列添加默认约束,默认值为当前日期ALTERTABLEEmployeesADDCONSTRAINTDF_JoiningDateDEFAULTGETDATE()FORJoi...
Article for:SQL Server▾ Query below lists all table (and view) constraints - primary keys, unique key constraints and indexes, foreign keys and check and default constraints. Query selecttable_view, object_type, constraint_type, constraint_name, detailsfrom(selectschema_name(t.schema_id) +'...
Learn more about the Microsoft.SqlServer.Management.SqlParser.SqlCodeDom.SqlDefaultConstraint.Microsoft.SqlServer.Management.SqlParser.SqlCodeDom.ISqlTableElement.IsColumnDefinition in the Microsoft.SqlServer.Management.SqlParser.SqlCodeDom n...
id INT PRIMARY KEY, `name` VARCHAR ( 255 ) ); CREATE TABLE stu_info ( id INT , stu_name VARCHAR ( 255 ) not null , gender CHAR ( 1 ) , seat INT , age INT DEFAULT 18, major_id int, CONSTRAINT pk_id PRIMARY KEY (id), ...
check(sex in ('男','女')),check(age>0) ); -- 单独添加主键 alter table test_emp3 add constraint pk_ename primary key(ename); -- 一次添加多个主键 -- 注意:1.一次添加多个主键,只能采取下列方式(使用GUI工具除外); -- 2.不能使用分别在eid和ename后面加primary key ...
The visibility of the metadata in catalog views is limited to securables that a user either owns, or on which the user was granted some permission. For more information, see Metadata Visibility Configuration. Examples The following example returns the definition of the DEFAULT constraint that...
[PRIMARY KEY]用于指定表的主键(即关系中的主属性),实体完整性约束条件规定:主键必须是唯一的,非空的; [,FOREIGN KEY (列名[,列名]...) REFERENCE<表名>(列名[,列名]...)]是用于指定外键参照完整性约束条件,FOREIGN KEY指定相关列为外键,其参照对象为另外一个表的指定列,即使用REFERENCE引入的外表中的列...
ServiceMasterKey 類別 ServiceQueueEvent 類別 ServiceQueueEventSet 類別 ServiceRequestException 類別 ServiceStartMode 列舉型別 Settings 類別 ShrinkMethod 列舉型別 SimpleObjectCollectionBase 類別 SmoApplication 類別 SmoApplication.AnyObjectEventHandler 委派 SmoApplication.DatabaseEventHandler 委派 SmoApplication.Object...
(繼承自 ISqlConstraint)。 ElementClass 取得項目的中繼資料類別。 (繼承自 IModelElement)。 ExpressionDependencies 取得預設值指令碼所參考的物件清單。 ExtendedProperties 取得此物件的擴充屬性清單。 (繼承自 ISqlExtendedPropertyHost)。 ForColumn 取得或設定套用預設條件約束的資料行。 IsDisabled 取得或設定值,...