How to query child to parent

Question

How to query child to parent like contact to parent..and how to query master lookup relations.

select id,lastnam,(select id,name from account where accountid=conatctid)from contact

Answer 1

This just an example on how the parent-child query works...

Ways of writing Parent - Child Queries for Standard Objects

Select Id, Name, (Select Id, LastName from Contacts where Lastname='Frank') from Account

Select Id, LastName, Account.Name from Contact

Ways of writing Parent - Child Queries for Custom Objects

Select Id, Name, (Select Id, Name from Custom_Object2s__r) from Custom_Object1__c

Select Id, Name, Custom_Object1__r.Name from Custom_Object2__c

Hope this might helps...

Answer 2

If you want get the parent object information then you need to use like this.

SOQL Child to Parent

for(Contact objContact: [SELECT Id, LastName, AccountId, Account.Name FROM Contact])
{
  system.debug('====Account Name======'+objContact.Account.Name);
}

if you want any other info about Account then you need to use Account.FieldAPIName... this way you will be able to get the Account info

SOQL Parent to child

for(Account objAccount: [SELECT Id, Name, (SELECT Id, LastName FROM Contacts)  FROM Account])
{
    for(Contact objContact: objAccount.Contacts)
    {
       system.debug('====Contact onfo======'+objContact);
    }
 }

Answer 3

You can traverse a relationship from a child object (contact) to a field on its parent (Account.Name) by using dot notation.

You can traverse multiple levels upwards!

List<Contact> list= [Select ID,LastName,Account.Name, Account.Industry from Contact where Name='abcd'];
   for(Contact c: list){
      System.debug('Contact LastName is:' + c.LastName);
      System.debug('Account Name is:' + c.Account.Name);
   }

Answer 4

we can understand it by an example. We have Account and Contact Object and we know that the relationship between them is lookup relationship. Note : This relationship has one property called cascadedelete that is why, when you will delete a contact, it's parent will got deleted.

Child To Parent SOQL ; [ SELECT Name,Phone,Email,AccountId,Account.Name,Account.Phone,Account.BillingAddress FROM Contact ]