Power Query - Data type conversion step, When in the query to do this?

[NAOS]

Hi all,

Quick question. Is it better to define the data type of columns in power query as soon as they are imported than doing it at the very end of the query? I imagine it would make a big difference as we would be giving the engine the data type that has to operate with, but I dont really know how Power query operates internally so this is just a guess.

Any ideas?

thanks!

[v-yulgu-msft]

Hi @NAOS ,

---

Is it better to define the data type of columns in power query as soon as they are imported than doing it at the very end of the query?

---

I think it depends on what transformation you apply to data model. Different data transformation might deal with data type in different way. 

I would suggest you use SQL Profile or Processor Monitor to trace performance.

Deep-dive into query performance with SQL Profiler and Power BI Desktop

Using Process Monitor To Troubleshoot Power Query Performance Issues With File Data Sources

Best regards,

Yuliana Gu