DataType Property

Applies To

Table field.

Description

You can use the DataType property to specify the type of data stored in a table field. Each field can store data consisting of only a single data type.

Setting

The DataType property uses the following settings.

Setting	Type of data	Size

Text	(Default) Text or combinations of text and numbers, as well as numbers that don't require calculations, such as phone numbers.	Up to 255 characters or the length set by the FieldSize property, whichever is less. Microsoft Access does not reserve space for unused portions of a text field.
Memo	Lengthy text or combinations of text and numbers.	Up to 65,535 characters. (If the Memo field is manipulated through DAO and only text and numbers [not binary data] will be stored in it, then the size of the Memo field is limited by the size of the database.)
Number	Numeric data used in mathematical calculations. For more information on how to set the specific Number type, see the FieldSize property.	1, 2, 4, or 8 bytes (16 bytes if the FieldSize property is set to Replication ID).
Date/Time	Date and time values for the years 100 through 9999.	8 bytes.
Currency	Currency values and numeric data used in mathematical calculations involving data with one to four decimal places. Accurate to 15 digits on the left side of the decimal separator and to 4 digits on the right side.	8 bytes.

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AutoNumber	A unique sequential (incremented by 1) number or random number assigned by Microsoft Access whenever a new record is added to a table. AutoNumber fields can't be updated. For more information, see the NewValues property.	4 bytes (16 bytes if the FieldSize property is set to Replication ID).
Yes/No	Yes and No values and fields that contain only one of two values (Yes/No, True/False, or On/Off).	1 bit.
OLE Object	An object (such as a Microsoft Excel spreadsheet, a Microsoft Word document, graphics, sounds, or other binary data) linked to or embedded in a Microsoft Access table.	Up to 1 gigabyte (limited by available disk space)
Hyperlink	Text or combinations of text and numbers stored as text and used as a hyperlink address. A hyperlink address can have up to three parts: displaytext — the text that appears in a field or control. address — the path to a file (UNC path) or page (URL). subaddress — a location within the file or page. The easiest way to insert a hyperlink address in a field or control is to click Hyperlink on the Insert menu.	Each part of the three parts of a Hyperlink data type can contain up to 2048 characters.
Lookup Wizard	Creates a field that allows you to choose a value from another table or from a list of values by using a list box or combo box. Clicking this option starts the Lookup Wizard, which creates a Lookup field. After you complete the wizard, Microsoft Access sets the data type based on the values selected in the wizard.	The same size as the primary key field used to perform the lookup, typically 4 bytes.

You can set this property only in the upper portion of table Design view.

In Visual Basic, you can use the DAO Type property to set a field's data type before appending it to the Fields collection.

Remarks

Memo, Hyperlink, and OLE Object fields can't be indexed.

Tip Use the Currency data type for a field requiring many calculations involving data with one to four decimal places. Single and Double data type fields require floating-point calculation. The Currency data type uses a faster fixed-point calculation.

Caution Changing a field's data type after you enter data in a table causes a potentially lengthy process of data conversion when you save the table. If the data type in a field conflicts with a changed DataType property setting, you may lose some data.

Set the Format property to specify a predefined display format for Number, Date/Time, Currency, and Yes/No data types.

For more information about choosing a field data type, see Chapter 4, "Working with Variables, Data Types, and Constants," in Building Applications with Microsoft Access 97.