private SqlExpr termsEqual(ValueExpr left, ValueExpr right)
throws UnsupportedRdbmsOperatorException
{
SqlExpr bnodes = eqIfNotNull(bNode(left), bNode(right));
SqlExpr uris = eqIfNotNull(uri(left), uri(right));
SqlCase scase = new SqlCase();
scase.when(or(isNotNull(bNode(left)), isNotNull(bNode(right))), bnodes);
scase.when(or(isNotNull(uri(left)), isNotNull(uri(right))), uris);
return literalEqual(left, right, scase);
}