Linked Columns and overloads of $ ! ?

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1

https://learninghub.kx.com/forums/topic/linked-columns-and-overloads-of

I am trying to figure out WHICH overloads of $ ! ? are used in foreign keys and linked columns syntax

Foreign Keys

kt$localColumn

Question 1. Is $ for enum ?

Question 2. kt as a table type is undocumented (but implied) right ?



LinkedColumn

otherTable!otherTable.otherCol?localColumn

Q3. Is ? doing a find

Q4. Is ! doing a dict (as in keyed table is a dict too) way OR "linking" which is undocumented still

Q doc still has some gaps which is why I have come up with these inferences after playing around with the code in the links below for a while. So ideally please gives "yes"/"no" or a big tutorial ;-)

Links

https://code.kx.com/q/kb/linking-columns/#splayed-tables

https://code.kx.com/q/wp/foreign-keys/#foreign-keys

2

The following page has some examples on the different types of enum operations: https://code.kx.com/q/basics/enumerations/

3

Q1. Yes, $ is creating an enum. https://code.kx.com/q/ref/enumerate/ . Could you supply a reproducible case for what the variables represent in the first statement.

Q2. KeyedTable (kt?) is documented see https://code.kx.com/q/kb/faq/#keyed-tables.

Q3. ? is doing a find. https://code.kx.com/q/ref/find/

t1

c1 c2

c 10

b 20

a 30

c3

sym$aba`c

t1.c1?c3

2 1 2 0



Q4. The ! is simply creating an enumeration. If you are then to update the table with the result of that query, it would be added to the table as a foreign key. Documentation exists here. https://code.kx.com/q/ref/enumeration/








`t1!t1.c1?c3








`t1!2 1 2 0








update link:t1!t1.c1?c3 from t2








`t2








meta t2








c | t f a


----| ------


c3 | s


c4 | f


link| j t1




The following page has some examples on the different types of enum operations: https://code.kx.com/q/basics/enumerations/