+/*
+ Check if gl_code is used by more than 2 tax types,
+ or check if the two gl codes are not used by any other
+ than selected tax type.
+ Necessary for pre-2.2 installations.
+*/
+function is_tax_gl_unique($gl_code, $gl_code2=-1, $selected_id=-1) {
+
+ $purch_code = $gl_code2== -1 ? $gl_code : $gl_code2;
+
+ $sql = "SELECT count(*) FROM "
+ .TB_PREF."tax_types
+ WHERE (sales_gl_code=" .db_escape($gl_code)
+ ." OR purchasing_gl_code=" .db_escape($purch_code). ")";
+
+ if ($selected_id != -1)
+ $sql .= " AND id!=".db_escape($selected_id);
+
+ $res = db_query($sql, "could not query gl account uniqueness");
+ $row = db_fetch($res);
+
+ return $gl_code2 == -1 ? ($row[0] <= 1) : ($row[0] == 0);
+}