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Determines whether an expression is blank.
ISBLANK(eExpression) |
Parameters
- eExpression
- Specifies the expression for ISBLANK(В ) to evaluate. eExpression can be a field in a table, a variable or array element, or an expression.
Return Value
Logical. ISBLANK(В ) returns True (.T.) if the expression eExpression is blank; otherwise, ISBLANK(В ) returns False (.F.).
ISBLANK(В ) returns True (.T.) for fields when those fields contain certain values. The following table lists the values that field types contain for ISBLANK(В ) to return True.
| Data type | Values the field contains |
|---|---|
|
Blob |
Empty (0h) or contains only zero bytes, for example, 0h00, 0h000000, and so on |
|
Character |
Empty string, spaces, or no value, such as a newly appended blank record or cleared with BLANK |
|
Date |
Blank date ({ / / }) or no value, such as a newly appended blank record or cleared with BLANK |
|
DateTime |
Blank datetime ({ / / : : }) or no value, such as a newly appended blank record or cleared with BLANK |
|
Float |
No value, such as a newly appended blank record or cleared with BLANK |
|
General |
Empty, for example, no OLE object |
|
Logical |
No value, such as a newly appended blank record or cleared with BLANK |
|
Memo |
Empty, for example, no memo contents |
|
Numeric |
No value, such as a newly appended blank record or cleared with BLANK |
|
Varbinary |
Empty (0h) or contains only zero bytes, for example, 0h00, 0h000000, and so on |
 Note: |
|---|
| Expressions with Currency, Integer, or Double type are never blank; therefore, ISBLANK(В ) always returns False (.F.) for these expression types. |
Remarks
To create a blank record, use the APPEND BLANK and BLANK commands. You can also use BLANK to clear data from fields in a record.
ISBLANK(В ) differs from EMPTY(В ) and ISNULL(В ). For example, EMPTY(В ) returns True (.T.) if a character expression evaluates to empty, for example, it contains spaces, tabs, carriage returns, or line feeds. ISBLANK(В ) returns True (.T.) if the character expression contains only the empty string ("") or spaces.
Example
In the following example, a table named mytable is created and a blank record is appended. ISBLANK(В ) returns True (.T.) because myfield is blank. A value is placed in myfield, and ISBLANK(В ) returns False (.F.) because myfield is no longer blank.
| В |  Copy Code |
|---|---|
CREATE TABLE mytable FREE (myfield C(20)) APPEND BLANK && Add new blank record CLEAR ? ISBLANK(myfield) && Displays .T. REPLACE myfield WITH 'John Smith' && Insert a value in the field ? ISBLANK(myfield) && Displays .F. | |