I have data in a table where there are "Buys" and "Sells" alongside the Quantity. I want query so that if it equals a "SELL" i multiply the Quantity column to negative. so far i am just selecting the data and taking from a certain timeframe. Nothing complex.
Using the update functionality along with the where clause you can edit a column in a table using certain filters. In this case the filter is where side=SELL.
If you add a backtick to the table name in the update statement this will update the table in place.
q)tab:([]time:10:00 12:00 13:00 14:00;side:`BUY`SELL`BUY`SELL;qty:300 400 300 500)
q)tab
time side qty
--------------
10:00 BUY 300
12:00 SELL 400
13:00 BUY 300
14:00 SELL 500
q)update qty:neg qty from tab where side=`SELL
time side qty
---------------
10:00 BUY 300
12:00 SELL -400
13:00 BUY 300
14:00 SELL -500
Updating in place:
q)update qty:neg qty from `tab where side=`SELL
`tab
q)tab
time side qty
---------------
10:00 BUY 300
12:00 SELL -400
13:00 BUY 300
14:00 SELL -500