Salesforce: Apex trigger to check whether email domain exists - triggers

Question

I want to find out whether the email domain exist in the database. Eg: If xxx#abc.com is going to be inserted, I want to check email with the same domain(abc.com) already exist or not. Following is the code to check the whole email exist.
trigger trig_Contact_webToContact on Contact (before insert)
{
final String errMsg = 'The email already exists on another Contact: ';
Set< String > emailSet = new Set< String >();
for( Contact c : Trigger.new ) emailSet.add( c.Email );
Map< String, Id > duplicateContactMap = new Map< String, Id >();
for( Contact c : [select Id, Email from Contact where Email = :emailSet] )
duplicateContactMap.put( c.Email, c.Id );
for( Contact c : Trigger.new ){
Id duplicateContactId = duplicateContactMap.get( c.Email );
if( duplicateContactId != null )
c.addError( errMsg + duplicateContactId );
}
}

Answer 1

First, get only domain from email, but not the whole email:
Set< String > emailDomainSet = new Set< String >();
for( Contact c : Trigger.new ) {
if (String.isBlank(c.Email)) continue;
int indexOfAt = c.Email.indexOf('#');
if (indexOfAt > 0) emailDomainSet.add( c.Email.substring(indexOfAt) );
}
then, in your case, you need to use query(queryString) method. Compose a SOQL string first
string queryString = 'select name from Contact where ';
string whereClause = ' ';
for (string domainItem : emailDomainSet) {
whereClause += ' or Email like \'%'+domainItem + '\' ';
}
whereClause = whereClause.substring(4);//remove first or in where clause
queryString += whereClause;
then, run it.
Instead of
for( Contact c : [select Id, Email from Contact where Email = :emailSet] )
you should put
for( Contact c : (List<Contact>)Database.query(queryString) )