also permits fast access to data when the primary key is used in queries. If a primary key constraint is defined on more than one column, values can be duplicated within one column, but each combination of values from all the columns in the primary key constraint definition must be unique....
MS Access stores relationship/foreign key information in an internal table calledMSysRelationships. That table is protected against read access even to the Admin user, so if you try to migrate without opening up access to it, you will get an error like this: [42000] [Microsoft][ODBC...
Phone-Pager-Primary photo Physical-Delivery-Office-Name Physical-Location-Object Picture PKI-Critical-Extensions PKI-Default-CSPs PKI-Default-Key-Spec PKI-Enrollment-Access PKI-Expiration-Period PKI-Extended-Key-Usage PKI-Key-Usage PKI-Max-Issuing-Depth PKI-Overlap-Period PKT PKT-Guid Policy-Replicati...
Copy Options: Right-click within the results grid to access options likeSelect All, Copy, Copy with Headers, and Copy Headers, making it convenient to transfer data for other uses. Save Query Results: Includes the ability to save query results to multiple formats such as JSON, Excel, and CS...
當您建立資料表時,可以建立 FOREIGN KEY 條件約束作為資料表定義的一部份。如果已經存在資料表,您可以加入 FOREIGN KEY 條件約束,前提是 FOREIGN KEY 條件約束已連結到其他或相同資料表中現有的 PRIMARY KEY 條件約束或 UNIQUE 條件約束。資料表可包含多個 FOREIGN KEY 條件約束。
(11) | PRIMARY KEY AUTO_INCREMENT | | height | int(11) | | | width | int(11) | | | comment | varchar(255) | | | compressed | boolean | | | orientation | varchar(255) | | | photoId | int(11) | FOREIGN KEY | +---+---+---+Save a one-to-one relationNow let's sa...
create Table Examination (e_id smallint primary key not null,l_language float, english float,computer float) --可以创建表时同时创建主键、外键 alter table examination add constraint FK_ID foreign key(student_id) references student(student_id) --当然也可以建立表后再建外键 ...
FOREIGN KEY约束仅能引用位于同一服务器上的同一数据库中的表。 跨数据库的引用完整性必须通过触发器实现。 有关详细信息,请参阅CREATE TRIGGER (Transact-SQL)。 FOREIGN KEY约束可引用同一表中的其他列,并称之为自引用。 在列级指定的FOREIGN KEY约束只能列出一个引用列。 此列的数据类型必须与定义约束的列的数...
For a given computer or user account, this attribute specifies the list of service principal names (SPN) corresponding to
获取MSSQLServer,Oracel,Access数据字典信息 1: 数据字典记录了数据库的系统信息,是只读表和视图的集合,数据字典的所有者为sys用户,并且存放在system表空间中。 数据字典基表存放基本信息,普通用户不能访问,只能通过访问数据字典视图取得系统信息,数据字典包含三种类型:...