CreateQuery dst (children 3)
 Identifier dst
 Columns definition (children 1)
  ExpressionList (children 3)
   ColumnDeclaration id (children 1)
    DataType UInt32
   ColumnDeclaration a (children 1)
    DataType Tuple (children 1)
     ExpressionList (children 2)
      NameTypePair col_a (children 1)
       DataType Nullable (children 1)
        ExpressionList (children 1)
         DataType String
      NameTypePair type (children 1)
       DataType String
   ColumnDeclaration b (children 1)
    DataType Tuple (children 1)
     ExpressionList (children 2)
      NameTypePair col_b (children 1)
       DataType Nullable (children 1)
        ExpressionList (children 1)
         DataType String
      NameTypePair type (children 1)
       DataType String
 Storage definition (children 2)
  Function MergeTree
  Identifier id
