Test on joins

To hit on the issue just fixed.

test/people_fjoin_personroom.query

@@ -0,0 +1 @@
+people⧓person_room

test/people_fjoin_personroom.result

@@ -0,0 +1,9 @@
+id,name,chief,age,room
+0,jack,0,22,1
+1,carl,0,20,4
+2,john,1,30,2
+3,dean,1,33,2
+4,eve,0,25,5
+5,duncan,4,30,1
+6,paul,4,30,5
+7,alia,1,28,1

test/people_join_personroom.query

@@ -0,0 +1 @@
+people⋈person_room

test/people_join_personroom.result

@@ -0,0 +1,9 @@
+id,name,chief,age,room
+0,jack,0,22,1
+1,carl,0,20,4
+2,john,1,30,2
+3,dean,1,33,2
+4,eve,0,25,5
+5,duncan,4,30,1
+6,paul,4,30,5
+7,alia,1,28,1

test/people_join_rooms.query

@@ -0,0 +1 @@
+people⧓person_room ⧓ rooms

test/people_join_rooms.result

@@ -0,0 +1,13 @@
+id,name,chief,age,room,phone
+0,jack,0,22,1,1516
+1,carl,0,20,4,1041
+2,john,1,30,2,1617
+3,dean,1,33,2,1617
+4,eve,0,25,5,9212
+5,duncan,4,30,1,1516
+6,paul,4,30,5,9212
+7,alia,1,28,1,1516
+---,---,---,---,"0","1515"
+---,---,---,---,"3","1601"
+---,---,---,---,"6","1424"
+---,---,---,---,"7","1294"

test/select_people_join_rooms.query

@@ -0,0 +1 @@
+σid=='---' (people⧓person_room ⧓ rooms)

test/select_people_join_rooms.result

@@ -0,0 +1,5 @@
+id,name,chief,age,room,phone
+---,---,---,---,"0","1515"
+---,---,---,---,"3","1601"
+---,---,---,---,"6","1424"
+---,---,---,---,"7","1294"