Explain about “Too Many SOQL Error: 101”

“System.LimitException: Too many SOQL queries: 101” 

This error occurs when you exceed SOQL queries governor limit. The actual limit is “you can run up to a total of 100 SOQL queries in a single call or context”.

How to resolve this “Error: System.LimitException: Too many SOQL queries: 101”

• To fix the issue, change your code so that the number of SOQL fired is less than 100.
• If you need to change the context, you can use @future annotation which will run the code asynchronously.
• Avoid SOQL queries that are inside FOR loops.

Follow the key coding principals for Apex Code:

1. Avoid SOQL queries inside For loop.

trigger accountTestTrggr on Account (before insert, before update)
{
  //This queries all Contacts related to the incoming Account records in a 
  // single SOQL query.
  //This is also an example of how to use child relationships in SOQL
  List<Account> accountsWithContacts = [select id, name, (select id, salutation, 
   description, firstname, lastname, email from Contacts) from Account where Id 
   IN :Trigger.newMap.keySet()];
   
  List<Contact> contactsToUpdate = new List<Contact>{};
  // For loop to iterate through all the queried Account records 
  for(Account a: accountsWithContacts)
  {
     // Use the child relationships dot syntax to access the related Contacts
     for(Contact c: a.Contacts)
     {
      System.debug('Contact Id[' + c.Id + '], FirstName[' + c.firstname + '],
       LastName[' + c.lastname +']');
      c.Description = c.salutation + ' ' + c.firstName + ' ' + c.lastname; 
      contactsToUpdate.add(c);
     }       
   }
      
   //Now outside the FOR Loop, perform a single Update DML statement. 
   update contactsToUpdate; 

}

2. Use @future Appropriate.

trigger accountAsyncTrigger on Account (after insert, after update) 
{
    //By passing the @future method a set of Ids, it only needs to be
    //invoked once to handle all of the data. 
    asyncApex.processAccount(Trigger.newMap.keySet());
}

Here is the Apex class that defines the @future method:

global class asyncApex 
{
  @future 
  public static void processAccount(Set<Id> accountIds)
  {
       List<Contact> contacts = [select id, salutation, firstname, lastname, 
       email from Contact where accountId IN :accountIds];
       for(Contact c: contacts)
       {
    System.debug('Contact First Name and Last Name: '+c.firstname+' 
          '+c.lastname);
    c.Description = c.salutation + ' ' + c.firstName + ' ' + c.lastname;
        }
        update contacts;
  }

}