CreateQuery test_isnull (children 3)
 Identifier test_isnull
 Columns definition (children 1)
  ExpressionList (children 3)
   ColumnDeclaration id (children 1)
    DataType UInt64
   ColumnDeclaration n.null (children 1)
    DataType UInt8
   ColumnDeclaration n (children 1)
    DataType Nullable (children 1)
     ExpressionList (children 1)
      DataType UInt64
 Storage definition (children 2)
  Function MergeTree
  Function tuple (children 1)
   ExpressionList
