Overview

Data types can seem confusing for example, if a field's data type is Text, it can store data that consists of either text or numerical characters. But a field whose data type is Number can store only numerical data. So, you have to know what properties are used with each data type.

A field's data type determines many other important field qualities, such as the following:

Which formats can be used with the field.

The maximum size of a field value.

How the field can be used in expressions.

Whether the field can be indexed.

A field's data type can be predefined or you will select a data type depending on how you create the new field. For example, if you create a field from the Datasheet view and:

Use an existing field from another table, the data type is already defined in the template or in the other table.

Enter data in a blank column (or field), Access assigns a data type to the field based on the values that you enter or you can assign the data type and format for the field.

On the Modify Fields tab, in the Fields & Columns group, click Add Fields, Access displays a list of data types that you can select from.

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When to use which data type

Think of a field's data type as a set of qualities that applies to all the values that are contained in the field. For example, values that are stored in a Text field can contain only letters, numbers, and a limited set of punctuation characters, and a Text field can only contain a maximum of 255 characters.

Tip: Sometimes, the data in a field may appear to be one data type, but is actually another. For example, a field may seem to contain numeric values but may actually contain text values, such as room numbers. You can often use an expression to compare or convert values of different data types.

The following tables show you the formats available for each data type and explain the effect of the formatting option.

Basic Types

Format

Use to display

Text

Short, alphanumeric values, such as a last name or a street address. Note, beginning in Access 2013, Text data types have been renamed to Short Text.

Number, Large Number

Numeric values, such as distances. Note that there is a separate data type for currency.

Currency

Monetary values.

Yes/No

Yes and No values and fields that contain only one of two values.

Date/Time, Date/Time Extended

Date/Time: Date and time values for the years 100 through 9999.

Date/Time Extended: Date and time values for the years 1 through 9999.

Rich Text

Text or combinations of text and numbers that can be formatted using color and font controls.

Calculated Field

Results of a calculation. The calculation must refer to other fields in the same table. You would use the Expression Builder to create the calculation. Note, Calculated fields were first introduced in Access 2010.

Attachment

Attached images, spreadsheet files, documents, charts, and other types of supported files to the records in your database, similar to attaching files to e-mail messages.

Hyperlink

Text or combinations of text and numbers stored as text and used as a hyperlink address.

Memo

Long blocks of text. A typical use of a Memo field would be a detailed product description. Note, beginning in Access 2013, Memo data types have been renamed to Long Text.

Lookup

Displays either a list of values that is retrieved from a table or query, or a set of values that you specified when you created the field. The Lookup Wizard starts and you can create a Lookup field. The data type of a Lookup field is either Text or Number, depending on the choices that you make in the wizard.

Lookup fields have an additional set of field properties, which are located on the Lookup tab in the Field Properties pane.

ESPERO QUE TE AYUDE

Answer:

1. 255

2. Auto number

3. Click the drop - down arrow on right of the column header.

hope it helps u....☺☺