Is there a way to set up an if/else statement within a flow depending on if a SQL query errors out? ...

Jason Motley

12/07/2021, 9:43 PM

Is there a way to set up an if/else statement within a flow depending on if a SQL query errors out? For example,

if(select * from table) = error then (alter table add column) else somethingelse

Kevin Kho

12/07/2021, 9:44 PM

Use the case task on this page this checks for a condition. If is evaluated during build time. You need something to evaluate during runtime

Jason Motley

12/07/2021, 9:45 PM

Just what I need, thank you

Jason Motley

12/07/2021, 10:08 PM

One other quick q @Kevin Kho - is there a way to quickly detect if there is a column already present in a destination table? Without querying information schema. I want to add a timestamp to ALL data in a SQL table but I'm only uploading 1 days worth at a time, and some tables might not already have the timestamp column in place

Jason Motley

12/07/2021, 10:08 PM

ex.

if (column last refresh exists) then (add refresh time) else (add column last refresh then add refresh time)

. I tried some IF EXISTS SQL but that didn't quite work

Kevin Kho

12/07/2021, 10:12 PM

I dont think this is a simple operation in SQL. I think you need to query information tables but I can be wrong

Jason Motley

12/07/2021, 10:13 PM

so provided the information schema is BLANK/null (i.e. no column), what would I want in that "if" statement within Prefect itself?

Jason Motley

12/07/2021, 10:13 PM

if length(results)=0 (null?), then "do stuff"?

Kevin Kho

12/07/2021, 10:14 PM

If there are no columns, I think so, but of course do this inside a task and use the

case

instead of

if

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