PostgreSQL Tcl Interface Documentation | ||||
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pg_null_value_string
sets or retrieves a string to
be returned in query results for fields whose value is NULL, making it
possible to distinguish between NULL values an values that are not null
but are comprised of an empty string. Without setting an alternative
null value with this or with pg_result's -null_value_string, it is
impossible to tell the difference between a NULL field value and one that
is not null but empty.