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It is possible to run query and the results inserted into an Apex list:

List<Opportunity> opportunities = [SELECT Opportunity.OwnerId, Opportunity.Probability, Owner.Name FROM Opportunity WHERE Opportunity.LastModifiedDate = LAST_N_DAYS:7];

Is it possible to return a Map? Where the key would be the OpportunityID and the value the Opportunity?

If not, what is the quickest way to convert to a map?

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3 Answers 3

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196

I know only one:

Map<ID, Contact> m = new Map<ID, Contact>([SELECT Id, LastName FROM Contact]);

Here is the doc: Maps of sObjects

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  • 3
    That's a much better way to do it. I updated your link since it was just taking me to the home page instead of the specific topic. Commented Dec 11, 2012 at 18:01
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    This is one to commit to memory. I use it all the time. Commented Dec 11, 2012 at 18:47
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    Also, a quick way to get a set of returned Ids from a query is similar.. using the above code, just do Set<Id> myIds = m.keySet(); Commented Dec 11, 2012 at 19:15
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    To clarify, this method can only be used to generate Maps using Id of the object you are querying as the key. If you want to use a different value as the key, you will have to iterate over the list returned by your query and put values into a Map. For instance, if you wanted to use AccountId as the key, you would need to do something like this: List<Opportunity> oppList = [Select Id, AccountId from Opportunity]; Map<Id,Opportunity> accOppMap = new Map<Id,Opportunity>(); for(Opportunity o : oppList){ accOppMap.put(o.AccountId,o); } Commented May 4, 2015 at 15:13
  • @mast0r link is again changed :) Commented Sep 16, 2015 at 7:13
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Alternatively, if you have a list already -- say you're in a situation where you need a map, but aren't in a mood to refactor your entire class to handle a map, you can convert your list of results to a map thusly:

Map<Id,OBJ_TYPE> mapFromList = new Map<Id,OBJ_TYPE>(List_object_variable);

This will generate a map from the list as if you'd queried directly into a map.

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-1

You can also try this if you are using global variable for map

map<id,Opportunity> mmap = new map<id, opportunity>(); list<opportunity> opplist = [select id,ReferralCustomer__c from Opportunity where ReferralCustomer__c != null limit 10]; mmap.putAll(new Map<Id, Opportunity>(opplist));
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  • This is the same as both of the existing answers from 10+ years ago, but with less information and more steps. The intermediate list you're using to store the results of the query is not required. Commented Apr 4, 2024 at 11:45
  • no,it is different as we are using global variable in it and you are correct we don't need a list but it is a simplified way of expressing the technicality. you can directly pass the query into the map instance. Commented Apr 6, 2024 at 11:08
  • we are not using any looping over here as well \ Commented Apr 6, 2024 at 11:10
  • The global variable distinction doesn't make any difference here (and global should generally be avoided unless you know it's required). Neither of the existing answers use loops. Commented Apr 6, 2024 at 12:30
  • I have that requirement where we need to use the map data in another method which needs a global variable to perform this. Commented Apr 7, 2024 at 14:47

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