CreateQuery X (children 3)
 Identifier X
 Columns definition (children 1)
  ExpressionList (children 3)
   ColumnDeclaration id (children 1)
    DataType Int32
   ColumnDeclaration x_a (children 1)
    DataType String
   ColumnDeclaration x_b (children 1)
    DataType Nullable (children 1)
     ExpressionList (children 1)
      DataType Int32
 Storage definition (children 2)
  Function MergeTree
  Function tuple (children 1)
   ExpressionList