CreateQuery Y (children 3)
 Identifier Y
 Columns definition (children 1)
  ExpressionList (children 3)
   ColumnDeclaration id (children 1)
    DataType Int32
   ColumnDeclaration y_a (children 1)
    DataType String
   ColumnDeclaration y_b (children 1)
    DataType Nullable (children 1)
     ExpressionList (children 1)
      DataType String
 Storage definition (children 2)
  Function MergeTree
  Function tuple (children 1)
   ExpressionList