how to concatenate list of strings into one long string kdb

Question

I have a list of strings like this

q)select id from temp
id                               
---------------------------------
,"_"                             
"01coin"                         
"0chain"                         
"0dog"                           
"0-knowledge-network"            
"0-mee"                          
"0vix-protocol"                  
"0x"                             
"0x0-ai-ai-smart-contract"       
"0x678-landwolf-1933"            
"0xanon"                         
"0xcoco"                         
"0xdao"                          
"0xgasless-2"                    
"0xgen"
...

I need it to look like this

"_,01coin,0chain,0dog,0-knowledge-network,0-mee,0vix-protocol,...etc..."

What is the best approach to concatenate such a list into a single string in kdb ? Should I turn my "strings" into `symbols and then vs :/ them ??? I got this far but I don't know how to turn this list of "strings"; into a single "string,..."

("_,";"01coin,";"0chain,";"0dog,";"0-knowledge-network,";"0-mee,";"0vix-protocol,"; ...)

Maurice Lim · Accepted Answer · 2025-03-06 05:55:08Z

3

This should work.

exec”,”sv id from temp
exec((”,”sv id),”,”)from temp / with a trailing ,

sv converts vector into a scalar. In this case a list of string into a string.

See: https://code.kx.com/q/ref/sv/

vs is the opposite.

edited Mar 6 at 5:55

answered Mar 6 at 5:22

Maurice Lim

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6 Comments

Maurice Lim Mar 6 at 5:26

If you want to join the list of strings that you have, you can simply raze (flatten) them. But based on your desired output, the answer I provided should work.

niken Mar 6 at 5:28

omg thank you x10 i forgot about raze , this did the trick: raze (exec (id,\:",") from temp)

Maurice Lim Mar 6 at 5:29

You’re welcome. Do note that your approach will have a , at the end of the string. If that is what you want. My answer does not, although using my method you can simply add the , at the end too.

Maurice Lim Mar 6 at 5:47

If you are using the list as a qsql filter. You don’t really need to manipulate it like that. You can simply use the list and use some of keywords like in <list of ids> for the filter.

rianoc Mar 6 at 10:17

Avoid creating large string queries, instead pass data across .e.g h({select from tab where id in x}; exec id from temp)

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