tree3.gv

// SELECT [ ESSN = '01' ] ( PROJECTION [ ESSN , PNAME ] ( WORKS_ON JOIN PROJECT ) )
digraph {
	name [label="SELECT [ ESSN = '01' ] ( PROJECTION [ ESSN , PNAME ] ( WORKS_ON JOIN PROJECT ) )" shape=rectangle]
	0 [label=" ESSN='01'"]
	1 [label=" ESSN ,PNAME"]
	2 [label="⋈"]
	3 [label=WORKS_ON]
	4 [label=PROJECT]
		0 -> 1
		1 -> 2
		2 -> 3
		2 -> 4
}