topic Using a query result in another query in ArcGIS API for Python Questions

Using a query result in another query

KerryKang — Thu, 23 Apr 2020 04:46:09 GMT

Hello all,

I am a GIS analyst and very new to Python API. I hope to get some advice on creating syntax.

Here is my scenario.

1. get the record count in feature layer. this will be used to grab the record with max object id. (the very last object id will be matched with row count always).

query_result1 = workingLayer.query(return_count_only=True)

query_result1

2. Using the result from #1 in another query. 'where' part is where I am having an issue with. I am not sure how I can use the result from #1 with the where syntax.

query_result2 = workingLayer.query(where = , out_fields='Region, Date')

I've tried with what I used to with arcpy...something like this. But not working.

whereClause = "'ObjectId=" + str(query_result1) + "'"

query_result2 = workingLayer.query(where = whereClause, out_fields='Region, Date')

Cheers,

Re: Using a query result in another query

WillHouston — Fri, 24 Apr 2020 15:29:41 GMT

From:

whereClause = "'ObjectId=" + str(query_result1) + "'"

This looks to me like your resulting where clause would be

'ObjectId=49'

Try it without the single quotes:

whereClause = "ObjectId=" + str(query_result1)

In general I prefer the string format so I can better see the final string, but the result should be the same:

whereClause = "ObjectId = {0}".format(query_result1)

Also depending on your database management system, the case of "ObjectId" ("OBJECTID") might matter.

Edit in case anyone else sees this and wonders why I suggested removing the single quotes: I made an assumption that the query function is building a database query by inserting that parameter. A basic query with a WHERE clause might be, "SELECT * FROM working_table WHERE ObjectId = 1". By putting that parameter in single quotes, the query language treats it as a string: "... WHERE 'ObjectId=49'", so it is looking to compare that to a text field in the database. The query language would expect "WHERE 'ObjectId=49' = some_text_field".

Different query languages might return all results, return no results, or return an error. That I'm not sure about.

Re: Using a query result in another query

KerryKang — Mon, 27 Apr 2020 21:55:25 GMT

It worked, thanks Will!

Re: Using a query result in another query

JoshuaBixby — Tue, 28 Apr 2020 13:57:21 GMT

If someone's response answers your question, please mark it correct to close out the question.