AMPscript lookup not returning value

Question

fairly easy question here I guess but I'm having problems with it.

So I was trying an AMPscript exercise in trailhead:

Also, can be found here as exercise 3: https://trailhead.salesforce.com/content/learn/modules/ampscript-for-nondevelopers/practice-using-ampscript

Now in my own environment, I tried this with different variables:

%%[
    Var @Subscriber_Key
    Set @Subscriber_Key = Subscriber_Key
    Var @CardNumber
    Set @CardNumber = Lookup("CARDS_DE","Card_Number","Subscriber_Key",@Subscriber_Key) 
]%%
    %%=v(CardNumber)=%%

I didn't get an error but it didn't return any values. I used the same structure to make this script as in example. Is there something I'm missing here? The attributes should be right.

Attributes in CARDS_DE: Card_Number, Subscriber_Key, Date_Created

Subscriber_Key is also in the "Master DE".

Answer 1

Found it. The problem is in your code, you've forgetten the @ character before CardNumber variable in the last line..

Try this:

%%[
    Var @Subscriber_Key
    Set @Subscriber_Key = Subscriber_Key
    Var @CardNumber
    Set @CardNumber = Lookup("CARDS_DE","Card_Number","Subscriber_Key",@Subscriber_Key) 
]%%
    %%=v(@CardNumber)=%%