System.Query Exception

Hi,

Any error related to query will give this exception.

for example:-

1. String not correctly setup in dynamic query - 'select id from contact where id = 'testId''

How to handle it-

When attempting to fetch a single record from the database it is easy to run into the above exception. I’ve seen two schools of thought in dealing with this issue – mostly in the forums – and have been hoping to find a more official standpoint.

I’ll describe the patterns and perhaps you can help me decide.

The Try-Catch Pattern

Surround your query by a try-catch block.
Fetch the record into a single object type variable.
Either the query successfully executes, or the exception is caught and you deal with it appropriately.
An example,

MyObject__c obj;

try{

obj = [SELECT id FROM MyObject__c WHERE name=:previouslyDefinedVar];

} catch(System.QueryException e){

// Perform logic here

}
The Only Use Lists For Query Results Pattern

Fetch records into Lists of objects. Do this even if you only expect a single row to be returned. [Queries that return values into Lists do not throw the above exception]
Check the size of the list(perhaps with an if-statement) and only perform required actions on the record if the list has a size of 1.
List<MyObject__c> objects = [SELECT id FROM MyObject__c WHERE name=:previouslyDefinedVar];

if(objects.size()==1){

// Perform Logic

}

Hope this helps.