qsql select from or condition gives error

[Michael]

When I try to run the following query against our dev box I get a type error. What is type?

q)select Sym,Reg,Alpha from equity_tab where Reg=`P2 or Alpha>10.
‘type

I tried changing the parameters round but get empty results when I know there should be some.
q)select Sym,Reg,Alpha from equity_tab where Alpha>10. or Reg=`P2
Sym Reg Alpha
————-

Do you know what’s going on?

~Mike

[admin]

q code is evaluated right to left. When you say:
select from t where a=1 or b=`c
What kdb is evaluating is:
select from t where a=(1 or (b=`c))
Which reduces to:
select from t where a=1

You can see this from the example below:

q)t:([] a:5?01b; b:5?`c`d)
q)t
a b
---
0 c
1 c
1 d
0 c
0 d
q)select from t where a=1 or b=`c
a b
---
1 c
1 d
q)select from t where a=(1 or b=`c)
a b
---
1 c
1 d

To make kdb behave how you expect place parentheses around a=1 like so:

q)select from t where (a=1) or b=`c
a b
---
0 c
1 c
1 d
0 c

There is a similar issue when using “and”, though mostly in kdb you will want to use comma to separate conditions rather than “and”.

[Author]

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