CODEWITHSUNDEEP
kdb+parameterization
man_of_dalmasca
man_of_dalmasca

Reputation: 49

Parameterizing a kdb q script

I'm writing a kdb/q script which will somehow have to prompt for user input and then add that input into several otherwise-preformatted queries. Suggestions on how to prompt/accept the input and parameterize the queries?

Upvotes: 2

Views: 1351

Answers (4)

nyi
nyi

Reputation: 3229

You can pass the input as command-line arguments too, using .z.x & .Q.opt :

$ q -item cam
q)p:.Q.opt .z.x
q)p`item
item| "cam"

q)select from tab where items=first `$p`item
items sales prices
------------------
cam   0     15

Upvotes: 4

Thomas Smyth
Thomas Smyth

Reputation: 5644

You can accept user input using read0 0, which waits will catch all a user types until they hit enter. The input will then be returned as a string. You can either type this into an active q session or wrap it up in a function like this:

q)f:{a:read0 0;show a}
q)f[]
12
"12"

In this case I have typed 12 which is returned as the string "12".

As for parameterising queries this can be done through strings, but this is not very q so to speak. You would be better to cast the inputs to another type and use functional form or even standard selects, for example:

q)tab:([]a:1 2 3 4)
q){input:"J"$read0 0;select from tab where a=input}[]
4
a
-
4

You can read more about functional form on the Kx wiki.

Upvotes: 3

Bartosz Kaliszuk
Bartosz Kaliszuk

Reputation: 131

For user input, you can use read0 on file handle 0 - standard input. User prompt would be printed to standard output (file descriptor 1) like this:

1 "Please give me some input: ";
input: read0 0;

For query parametrization, you can go either with string concatenation of functional query form as described here (code.kx.com)

Upvotes: 2

nyi
nyi

Reputation: 3229

Checkout read0 to read the inputs from console.

q)rl:{1">> "; value "select from tab where items=`",read0 0}
q)rl`
>> cam
items sales prices
------------------
cam   0     15

Upvotes: 2

Related Questions