How to update an item in a SharePoint list based on the changes from another SharePoint List?

[wimmste]

I have two lists  a Person List and a Course List.

I need to count down 1 in the "Seats" Column when the "AC Date" is choosen in the Person List, so i know how many Seats are left in the course.

The "AC Date" Column is a lookup from Course List.

"ACDateLocation" is a Single line Text Column.

I would be very happy about your help.

[yashag2255]

Hi @wimmste 

Please refer to the screenshot below and replicate

Expression used for Seats 

add(body('Get_item')?['Seats'],-1)

The ID in update Item is referring to the ID retrieved from the Get Item action. 

Hope this Helps!

If this reply has answered your question or solved your issue, please mark this question as answered. Answered questions helps users in the future who may have the same issue or question quickly find a resolution via search. If you liked my response, please consider giving it a thumbs up. THANKS!

[wimmste]

Cool fast response thank you.

But whats the "length(...)" expression for the Condition ?

[yashag2255]

Hey @wimmste 

Sorry I missed that in the previous response, the expression used is 

length(triggerBody()?['Courer']?['Value'])

Here I am checking if there is some value in the lookup field. You can type length in the expression editor and select the Course Value from the dynamic selector (within the bracket of the length function)

Hope this Helps!

[wimmste]

@yashag2255 

i get an Error in the Condition:

InvalidTemplate. Unable to process template language expressions for action 'Condition' at line '1' and column '46741': 'The template language function 'length' expects its parameter to be an array or a string. The provided value is of type 'Null'. Please see https://aka.ms/logicexpressions#length for usage details.'.

My Condition:

length(triggerbody()?['AC_x0020_Date']?['Value'])

My Flow:

[yashag2255]

Hi @wimmste 

Please update the flow condition as shown in the screenshot

Expression:

empty(triggerBody()?['Courer']?['Value'])

The condition is not equal to and the value on right side is true (type in the expression editor and select the value true)

Hope this Helps!

[wimmste]

@yashag2255 

Thx for your patience, i am really new to this complex Flows 😉

The Flow is counting down everytime i am updating or adding a item in the person List.

It should be 4 Seats on all Items in the Course List.

Maybe i need a help column so the workflow knows that it already count down for that Item in the person list.

My Flow now:

[yashag2255 · Accepted solution]

Hi @wimmste 

Yes! So the flow currently counts down every time you have modified/created the item and there is any value in the courses column (Based on your request initially). For the dyamically changing values, you will have to build equivalent logic in the flow to count for events such as multiple edits on an item not related to the course lookup, change in the selection of the course lookup etc. 

In this case, I would suggest you to use a calculated field in sharepoint itself instead of using flow (to make things easier)

Hope this Helps! 

[wimmste]

Thx i will try that now.