NULL_VALUE Function
Syntax
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:
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>
See Also