Cannot access the value of the kdb table column

Question

I am new to KDB and cannot understand why i can access the order column for the table stocks but not trader. The below is my code with the error.

q)trader
item     brand | price order
---------------| -----------
soda     fry   | 1.5   200
bacon    prok  | 1.99  180
mushroom veggie| 0.88  110
eggs     veggie| 1.55  210
tomatoes veggie| 1.35  100
q)trader.order
'order
  [0]  trader.order
       ^
q)stock.order
50 82 45 92
q)stock
item     brand  price order
---------------------------
soda     fry    1.5   50
bacon    prok   1.99  82
mushroom veggie 0.88  45
eggs     veggie 1.55  92
q)trader.order
'order
  [0]  trader.order
       ^

Answer 1

Your table trader is keyed and you cannot use trader.order to select the order column.

You can use this instead if you want

(0!trader)`order

The reason is because when you do trader.order what you actually do is you use indexing. It's the same as if you'd do list.index. A table is just a list of dictionaries and you use dot(.) to index into it. However a keyed table does not have the same structure so you'll have to unkey it first.