Newbie questions on KDB Table

Community Support
1

2 newbie questions on KDB tables, stuff I could not find in q-for-mortals and kdbfaq: 

  1. When inserting into KDB table I often have columns whose values are null. For e.g. if I have columns a, b, c and d I only insert to a & b at times or a & c etc. But KDB is not letting me do that - I keep getting error. Is there a way to fix this? 
  2. How do I give a default value to a column if not explicitly inserting? This as you can see is a direct corollary of question 1. 

Thanks!

2

Hi,

Inserts where columns contain null values should work:

q)t:( a:1 2; b:3 4.; c:po)
q)t insert ([] a:1 2; c:il) 2 3 q)t insert ( a:1 2; b:1.1 2.2)
4 5
q)`t insert ( b:1.1 2.2)
6 7
q)t
a b   c

1 3   p
2 4   o
1     i
2     l
1 1.1
2 2.2
  1.1
  2.2

Have you got an example for some code that was giving an error?

The carat^ symbol allows replacing nulls easily, for example:

q)update 9^a, 9.99^b, `ggg^c from t
a b    c

1 3    p
2 4    o
1 9.99 i
2 9.99 l
1 1.1  ggg
2 2.2  ggg
9 1.1  ggg
9 2.2  ggg

Either update the data as your inserting or as your retrieving.

Regards,
Ryan

--

TimeStored.com - KDB+ Training, Consulting, Software

On 15/09/2013 19:24, kdb newb wrote:

2 newbie questions on KDB tables, stuff I could not find in q-for-mortals and kdbfaq: 

  1. When inserting into KDB table I often have columns whose values are null. For e.g. if I have columns a, b, c and d I only insert to a & b at times or a & c etc. But KDB is not letting me do that - I keep getting error. Is there a way to fix this? 
  2. How do I give a default value to a column if not explicitly inserting? This as you can see is a direct corollary of question 1. 

Thanks!

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