Explain EXPLAIN QUERY TREE (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 5)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier t1
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t2
      TableJoin
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t3
      TableJoin
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t4
      TableJoin
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t5
      TableJoin
    Function and (children 1)
     ExpressionList (children 3)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t2.a
        Identifier t3.a
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t1.b
        Identifier t5.b
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t4.a
        Identifier t5.a
