Get the industry otherwise sphere that you want to identify since the key secret

Get the industry otherwise sphere that you want to identify since the key secret

To select one profession, click the line selector with the desired job. To select several industries, hold-down new Ctrl trick, and then click brand new row selector for every career.

If you like the order of your sphere inside the a simultaneous-career top the answer to vary from your order ones sphere on table, mouse click Indexes into the toolbar to exhibit the fresh new Indexes dialogue package, following reorder the field brands into directory entitled PrimaryKey.

Referential stability

Referential stability was a network out of guidelines you to definitely Supply spends so you’re able to make certain relationship ranging from records from inside the related tables are valid, and you don’t eventually erase otherwise changes relevant research. You could potentially put referential ethics whenever the pursuing the criteria is true:

  • New complimentary profession in the no. 1 dining table are a primary secret otherwise has a unique index.
  • New associated fields have a similar studies type. There are two exceptions. An AutoNumber job are related to lots field you to definitely have an excellent FieldSize property form off A lot of time Integer, and you can an enthusiastic AutoNumber profession who’s a good FieldSize possessions form of Duplication ID might be pertaining to several profession who has got a good FieldSize possessions form regarding Duplication ID.
  • Each other dining tables end up in a comparable Access database. Should your tables is actually linked tables, they have to be tables when you look at the Access style, therefore have to open the latest databases where he could be held setting referential ethics. Referential ethics can not be implemented for connected dining tables off database for the almost every other formats.
  • You simply cannot go into a regard throughout the overseas secret world of the related desk that doesn’t occur in the main key of the number one table. not, you could potentially enter a great Null worth regarding the international trick. That it specifies your facts try unrelated. Including, you can not enjoys your order that is assigned to a customers who not are present. not, you’ll have your order that’s allotted to no body of the typing a Null value regarding the CustomerID job.
  • You can not remove an archive away from a primary table if matching info can be found in a connected table. For example, you simply can’t erase an employee checklist regarding the “Employees” table when the discover purchases allotted to the employee about “Orders” table.
  • You cannot transform a first key well worth regarding the priple, you cannot transform an enthusiastic employee’s ID about “Employees” desk if there are instructions assigned to one to personnel in the “Orders” table.

Streaming position and you may deletes

Getting matchmaking in which referential integrity try implemented, you can establish if you prefer Access to instantly cascade modify otherwise cascade delete associated records. For many who lay this type of options, delete and update procedures who would constantly be prevented of the referential integrity rules was permitted. Once you erase ideas or alter number 1 trick thinking inside the a number 1 dining table, Accessibility helps make the necessary transform so you can associated tables in preserving referential integrity.

If you mouse click to search for the Cascade Up-date Related Fields examine field when you identify a relationship, any moment which you alter the primary key out of a record in the primary http://www.datingranking.net/cs/apex-recenze dining table, Microsoft Availableness immediately condition an important the answer to the newest well worth in all related records. Instance, if you alter a consumer’s ID on “Customers” table, brand new CustomerID industry in the “Orders” table is actually instantly upgraded for every single among that customer’s commands so the relationships isn’t broken. Availability cascades updates in place of showing one content.

If your no. 1 type in the key dining table try a keen AutoNumber career, choosing the Cascade Up-date Relevant Sphere look at container does not have any impression as you don’t replace the well worth within the an enthusiastic AutoNumber occupation.

Leave a Reply

Your email address will not be published. Required fields are marked *