CreateQuery bugcheck1 (children 3)
 Identifier bugcheck1
 Storage definition (children 2)
  Function MergeTree
  Function tuple (children 1)
   ExpressionList
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 1)
    ExpressionList (children 2)
     Literal \'c1\' (alias column_a)
     Literal \'c2\' (alias column_b)
