1 SET 2+ , 2 transition-variable = 2.1 expression 2.1 NULL 2.1 DEFAULT 2 ( 2.1+ , 2.1 transition-variable 2.2 ) = ( 2.2.1.0.0+ , 2.2.1.0.0 expression 2.2.1.0.0 NULL 2.2.1.0.0 DEFAULT 2.2.1.0.1 (1) 2.2.1.0 row-fullselect (2) 2.2.2 )