KDB boolean null value

Question

I am using the KDB C Api to write data into few KDB tables.

There is the need to insert in our tables null values.

I found all the null values I need for different types except for boolean.

Is there such thing within KDB?

I possibly would like to avoid using Integers as substitute as it would be too big.

Thanks

ki(ni);   // create null integer
kf(nf);   // create null double
kb(????); // how to create null boolean ??

Are you sure kdb+ supports null boolean values? code.kx.com/q/basics/datatypes - neither byte nor boolean are nullable types. — 3CEZVQ
– 3CEZVQ, Commented Jun 17 at 8:43
Thanks . I was trying to look for a null value in the KDB C header file k.h. I simply noticed that the value was missing. I asked to expert in case I had to create this bool null value in some other way. I missed that link on datatypes. Thanks. — Abruzzo Forte e Gentile
– Abruzzo Forte e Gentile, Commented Jun 18 at 4:12

rianoc · Accepted Answer · 2025-06-17 09:48:18Z

3

There is no boolean null in kdb+. Only true 1b, and false 0b.

https://code.kx.com/q/basics/datatypes/

The short datatype exists which is 2 bytes in size.

https://code.kx.com/q/interfaces/capiref/

kh(nh)

edited Jun 17 at 9:48

answered Jun 17 at 9:08

rianoc

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2 Comments

Abruzzo Forte e Gentile Jun 18 at 4:16

Perfect. Thank you very much for the straight answer. Actually I did not check about the storage as I wrongly assumed that boolean were a single byte data...looks I made the wrong assumption. Thanks again.

rianoc Jun 19 at 10:14

kc(" ") null character is 1 byte so technically the smallest datatype you could use. "\000" as an option for False - and any other character starting at "\001" for True. Feels a bit clunky though so unless absolute efficiency is needed the directly numeric short type is more intuitive if you must have a null option.

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