# Linked Columns and overloads of $ ! ? **URL:** \ **Category:** Community Support\ **Tags:** imported, kdb-and-q\ **Created:** [July 15, 2024, 2:06am UTC](https://forum.kx.com/t/linked-columns-and-overloads-of/13988 "2024-07-15T02:06:29Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![newstudent2017](https://avatars.discourse-cdn.com/v4/letter/n/a5b964/32.png) [@newstudent2017](https://forum.kx.com/u/newstudent2017)\ **Post date:** [July 15, 2024, 2:06am UTC](https://forum.kx.com/t/linked-columns-and-overloads-of/13988/1 "2024-07-15T02:06:29Z")
[https://learninghub.kx.com/forums/topic/linked-columns-and-overloads-of](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 ---
**Author:** ![amcdonald3](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@amcdonald3](https://forum.kx.com/u/amcdonald3)\ **Post date:** [July 15, 2024, 3:20pm UTC](https://forum.kx.com/t/linked-columns-and-overloads-of/13988/2 "2024-07-15T15:20:15Z")
The following page has some examples on the different types of enum operations: [https://code.kx.com/q/basics/enumerations/](https://code.kx.com/q/basics/enumerations/) ---
**Author:** ![amcdonald3](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@amcdonald3](https://forum.kx.com/u/amcdonald3)\ **Post date:** [July 15, 2024, 3:51pm UTC](https://forum.kx.com/t/linked-columns-and-overloads-of/13988/3 "2024-07-15T15:51:01Z")
Q1. Yes, `$` is creating an enum. [https://code.kx.com/q/ref/enumerate/](https://code.kx.com/q/ref/enumerate/) . Could you supply a reproducible case for what the variables represent in the first statement. Q2. KeyedTable (kt?) is documented see [https://code.kx.com/q/kb/faq/#keyed-tables](https://code.kx.com/q/kb/faq/#keyed-tables). Q3. `?` is doing a find. [https://code.kx.com/q/ref/find/](https://code.kx.com/q/ref/find/) > > > t1 c1 c2 * * * c 10 b 20 a 30 > > > c3 `sym$`a`b`a`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/](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/](https://code.kx.com/q/basics/enumerations/)