Re: Issue with Order in the by statement

[rocuinneagain]

Link to your original post for reference:

•  https://community.kx.com/t5/KX-Academy/Issues-with-Queries-and-qSQL/td-p/14099

You can test yourself and compare time and memory usage:

• https://code.kx.com/q/basics/syscmds/#ts-time-and-space
• https://code.kx.com/q/wp/columnar-database/
• https://code.kx.com/q/ref/set-attribute/

 

//Try and time the queries to compare 
\ts select last price by hour:60 xbar time.minute, sym from trade 
\ts select last price by sym,hour:60 xbar time.minute from trade 

//If they run very fast you can run them N number of times to get more accurate result 
//Running 100 times here 
\ts:100 select last price by hour:60 xbar time.minute, sym from trade 
\ts:100 select last price by sym,hour:60 xbar time.minute from trade 

//Attributes are useful in kdb+ 
//Apply grouped on sym and test 
update `g#sym from `trade 
\ts:100 select last price by hour:60 xbar time.minute, sym from trade 
\ts:100 select last price by sym,hour:60 xbar time.minute from trade 

//Removed grouped and test again 
update `#sym from `trade 
\ts:100 select last price by hour:60 xbar time.minute, sym from trade 
\ts:100 select last price by sym,hour:60 xbar time.minute from trade