Explain EXPLAIN QUERY TREE (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Function count (children 1)
      ExpressionList
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier x
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier y
      TableJoin (children 1)
       Function or (children 1)
        ExpressionList (children 2)
         Function equals (children 1)
          ExpressionList (children 2)
           Identifier x.A
           Identifier y.A
         Function and (children 1)
          ExpressionList (children 2)
           Function equals (children 1)
            ExpressionList (children 2)
             Identifier x.B
             Identifier y.B
           Function or (children 1)
            ExpressionList (children 2)
             Function and (children 1)
              ExpressionList (children 2)
               Function equals (children 1)
                ExpressionList (children 2)
                 Identifier x.C
                 Identifier y.C
               Function equals (children 1)
                ExpressionList (children 2)
                 Identifier x.D
                 Identifier y.D
             Function and (children 1)
              ExpressionList (children 2)
               Function equals (children 1)
                ExpressionList (children 2)
                 Identifier x.C
                 Identifier y.C
               Function equals (children 1)
                ExpressionList (children 2)
                 Identifier x.E
                 Identifier y.E
