# linking column to different tables **URL:** \ **Category:** Community Support\ **Tags:** kdb-and-q\ **Created:** [October 31, 2012, 8:40am UTC](https://forum.kx.com/t/linking-column-to-different-tables/7980 "2012-10-31T08:40:00Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Sam11](https://avatars.discourse-cdn.com/v4/letter/s/c6cbf5/32.png) [@Sam11](https://forum.kx.com/u/Sam11)\ **Post date:** [October 31, 2012, 8:40am UTC](https://forum.kx.com/t/linking-column-to-different-tables/7980/1 "2012-10-31T08:40:00Z")
Hello, I have a base table and multiple details table. I want to link a column of my base table to one of the details tables based on the column entry. For example, q)t1:( id:104 105; t:`a`b; v:4.4 5.5) q)ta:(id:enlist 104; w:`aa) q)tb:(id:enlist 105; w:`bb) Now I want to create a link tlink in t1 that will link t1.id to t2.id if t=`a and t1.id to t2.id if t=`b. This seems a bit far fetched but is this at all possible? If not, then I will create different versions of table t1 for each value of t. ---
**Author:** ![Aaron\_Davies](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Aaron\_Davies](https://forum.kx.com/u/Aaron_Davies)\ **Post date:** [November 4, 2012, 11:51pm UTC](https://forum.kx.com/t/linking-column-to-different-tables/7980/2 "2012-11-04T23:51:00Z")
To: personal-kdbplus@googlegroups.comX-Mailer: Apple Mail (2.1278)\> I have a base table and multiple details table. I want to link a column of my base table to one of the details tables based on the column entry.\> \> q)t1:( id:104 105; t:`a`b; v:4.4 5.5)\> q)ta:(id:enlist 104; w:`aa)\> q)tb:([]id:enlist 105; w:`bb)\> \> Now I want to create a link tlink in t1 that will link t1.id to t2.id if t=`a and t1.id to t2.id if t=`b.i don’t think this is doable while staying in 3nflinking columns have to link to a single table to workyou could of course put the details in key-value form instead:q)td:(id:104 105;t:`a`b;w:`aa`bb)q)update tlink:`td!(`id`t#td)?([]id;t)from`t1;q)t1id t v tlink---------------104 a 4.4 0 105 b 5.5 1 q)update tlink.w from t1id t v tlink w ------------------104 a 4.4 0 aa105 b 5.5 1 bbq)but that may or may not gain you anything over just having w in t1 in the first place ---
**Author:** ![raytork](https://avatars.discourse-cdn.com/v4/letter/r/e0b2c6/32.png) [@raytork](https://forum.kx.com/u/raytork)\ **Post date:** [November 5, 2012, 2:04am UTC](https://forum.kx.com/t/linking-column-to-different-tables/7980/3 "2012-11-05T02:04:00Z")
charset=us-ascii Message-Id: \<7CBC86A3-B898-4449-8155-38878E4905EF@gmail.com\> Cc: “[personal-kdbplus@googlegroups.com](mailto:personal-kdbplus@googlegroups.com)” X-Mailer: iPad Mail (10A403) From: Ray Subject: Re: [personal kdb+] linking column to different tables Date: Sun, 4 Nov 2012 21:04:20 -0500 To: “[personal-kdbplus@googlegroups.com](mailto:personal-kdbplus@googlegroups.com)” This is a fairly common usage in SQL and could be done inside a subquery sin= ce the problem posed implies that the id values are unique, e.g.=20 select x.id, x.text, s.text from tx x=20 join=20 (select y.id, y.text=20 from ty y union select z.id, z.text from tz z ) s on s.id =3D.x.id ---
**Author:** ![Sam11](https://avatars.discourse-cdn.com/v4/letter/s/c6cbf5/32.png) [@Sam11](https://forum.kx.com/u/Sam11)\ **Post date:** [November 6, 2012, 11:08pm UTC](https://forum.kx.com/t/linking-column-to-different-tables/7980/4 "2012-11-06T23:08:00Z")
Thanks for the replies. Yeah this was a ridiculous question. I ended up just creating multiple tables with common key columns that they can be joined against. Tans