Setting a NULL Indicator (Embedded SQL Guide)
From InterBase
If a parameter or select-list item can contain a NULL
value, the sqlind
field is used to indicate its NULL
status. Appropriate storage space must be allocated for sqlind
before values can be stored there.
On insertion, set sqlind
to –1 to indicate that NULL
values are legal. Otherwise set sqlind
to 0.
On selection, a sqlind
of –1 indicates a field contains a NULL
value. Other values indicate a field contains non-NULL
data.