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Referential Integrity


Referential integrity is implemented to ensure that the relationship between the primary key and the foreign key table is maintained. When referential integrity has been enforced between two tables, you can:
  1. Cascade Update Related Fields - This enables a change in the value of the primary key field to be automatically updated in all the tables where the field has been declared a foreign key.
  2. Cascade Delete Related Records - This enables the automatic deletion of all related records when the primary key record is deleted.

Arrangement of Data in the Table

Sorting Data - It helps in arranging the data in a systematic order for grouping and quick search. You can sort a table by columns, single or multiple, in an ascending or descending order.

Filtering Data - It enables us to display only those records in a table that meet a specified filter criterion. Assume that you have a table that contains data about all the customers and the regions they belong to. You now require information only about the customers in the northern region. A filter can enable you to specify the filter criterion as North and only those records of data matching the criterion will be displayed.

Access provides the following two methods to filter data:
  1. Filter by Selection - This method is used to filter the table based on a value in the table. For example, to find all customers from the northern region, you can select North from the table and click a button to display the required data.
  2. Filter by Form - This method is used to filter data based on a user - defined criterion. For example, to find all products having unit price greater than 50, you can type >50 and click a button to display the required data.
  3. Filter Excluding Selection - This method is used to filter the table based on a value in the table. For example, to find all customers from all the regions other than customers from the northern region, you can select North from the table and click the Filter Excluding Selection option. This filter is opposite to Filter by Selection.
  4. Advanced Filter/Sort - This method is used when you do not want to use any of the filters provided by Access and want to create you own filter/sort criterion based on a number of columns in the table.




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