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A data type is stored different types of values in a column in a table. For example, the data type of the column Customer Name that contains names of all the customers will be text and the data type of the column phone no. that contains the phone numbers of the customers will be number in the customers table.


Various Data Types in Access
  1. Text - This data type stores text or a combination of text and numbers. It can also be numbers that do not require calculations like the zip code.
  2. Memo - This data type stores a large number of text and numeric characters like notes or description of fields, or addresses.
  3. Number - This data type stores numeric data that is sued for mathematical calculations, except calculations involving money.
  4. Date/Time - This data type stores date and time value.
  5. Currency - This data type stores currency values
  6. Auto Numbers - This data type enables you to automatically insert numbers in a sequential or a random order.
  7. Yes/No - This data type is used for fields that can contain Yes/No, True/False, and On/Off values.
  8. OLE Object - This data type enables you to store objects like Word documents, Excel spreadsheet, pictures or sounds.
  9. Hyperlink - This data type enables you to store a hyperlink like an e-mail address or a Web site address.
  10. Lookup Wizard - This data type creates a field that enables you to select a field from another table. For example, while entering data in the Transaction table, you can use the Lookup Wizard to get the customer data from the Customers table.

Primary Key

We have discussed earlier that each object must be separately identified and it was further discussed in the context of employees that each of them be identified with a unique identifier. Similarly, while storing data in the Customers table, it should be ensured that each customer is assigned a unique identification number. This will ensure that customers with the same name are identified by using the unique customer identification number in the table. This unique number is known as the Primary Key of the table.

The Primary key ensures that there are no duplicate rows in a table. Every table must have a column that uniquely identifies each row in the table. Consider the following tables:

Customers Table


Customer ID

Customer Name


Phone No


A K & Co

B-58, Lalpat Nagar, New Delhi



S K Associates

D-85,Laxmi Nagar, New Delhi



Chopra & Khanna

A-95, Vikiram Vihar, New Delhi



In this table, customer ID is known as the Primary Key.

Service Table


Customer ID

Service ID


Type of Service

Total Fee Amount




Return Filing










TDS Return Filing


In this table, Service ID is known as the Foreign Key.


Customer Id is also a field in the Service table. This ensures that services are provided only to valid customers. When a primary key of a table appears as a field in another table, it is known as foreign key. A foreign key is created to maintain data integrity. When a primary key contains a combination of one or more fields, it is called a Composite key. In this table, a combination of the Customer Id and Product Id makes a row of data in the table unique.

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