NULL_VALUE Function

Syntax

A NULL_VALUE()

Returns

resultAny Type: Returns a null value. Not supported for numeric Xbasic variables.

Description

Assign a null value to any data type.

Discussion

NULL_VALUE() is used in an Update Operation or an Xbasic script to assign null to a DBF field or Xbasic variable.

For example, to assign a NULL value to a DBF Field:

dim t as P
t = table.open("orders")
t.change_begin()
t.date = NULL_VALUE()
t.change_end(.T.)
t.close()

NULL_VALUE() cannot be used to set a null value in a SQL::Arguments object. Use SQL::Arguments setNull().

Numeric variables are a special case. You cannot use NULL_VALUE() with a numeric variable. However, if you have a numeric field in a DBF table, you can set the field value to NULL_VALUE().

dim t as P
t = table.open("journal")
? t.PERIOD_YEAR
= 34
t.change_begin()
t.PERIOD_YEAR = NULL_VALUE()
t.change_end(.t.)
t.close()
? t.PERIOD_YEAR
= 0

While the numeric field, t.PERIOD_YEAR, reported 0 as it's value in the example above, if you look at the table in browse mode where NULL_VALUE() was assigned to a numeric field, no value will be visible in the field.

Xbasic Variable Null Values

When assigned to an Xbasic variable, NULL_VALUE() returns the following:

Interactive Window results of assigning null_value() to Xbasic variables

dim vA as a = null_value()
? vA
= <Has no sub-properties>

dim vB as b = null_value()
? vB
= 

dim vC as c = null_value()
? vC
= ""

dim vD as d = null_value()
? vD
= {  /  /    }

dim vF as f = null_value()
? vF
= <No data returned>

dim vL as l = null_value()
? vL
= .F.

dim vN as n = null_value()
? vN
= 0

dim vP as p = null_value()
? vP
= <Has no sub-properties>

dim vT as t = null_value()
? vT
= 

dim vU as u = null_value() 
? vU
= <Has no sub-properties>