article Keep Left or exists in Qlik Learning Documents

Keep Left or exists

syukyo_zhu — Mon, 22 Sep 2014 13:26:10 GMT

Keep Left or exists. which is more performant?

I will limit my second data table based with the result of my first table. I can use either left keep or Where exists in my second table

So,

Solution1

Table1:

Load mykey from mytableA;

Table2

Load * from mytableB Where exists (mykey);

Solution 2

Table1:

Load mykey from mytableA;

Table2

Keep left (Table1) Load * from mytableB;

Result: Solution 1 is 2 times faster than solution 1

In my example, MytableB have 9 million records

So Exists is more performant than " left keep".

Re: Keep Left or exists

robert99 — Mon, 22 Sep 2014 15:46:01 GMT

Solution 2

Table1:

Load mykey from mytableA;

Table2

left keep (Table1) Load * from mytableB;

what about the above speed wise. As isn't left keep and where exists doing the same thing

Re: Keep Left or exists

syukyo_zhu — Tue, 23 Sep 2014 13:30:10 GMT

Hi,

yes, the both do the same thing. i want juste show in my exemple "where exists" is more performant than "left keep". if you should reduce your table with 20 millons record with le resultat of your other table. you should use "where exist" and not "left keep".

Re: Keep Left or exists

robert99 — Tue, 23 Sep 2014 13:45:57 GMT

OK Thanks. Version 2 is clear. I assume version 2 was how you did the test not version 1?

Re: Keep Left or exists

syukyo_zhu — Tue, 23 Sep 2014 13:51:21 GMT

yes, i did a mistake in my first version, thanks for your remark.