Without trigger , workflow , validation.......
By using Duplicate Management we can restrict end user not to allow duplicate records
The criteria used to compare records and identify the possible duplicates are defined by a matching rule.
Next, a list of possible duplicates is returned (2).
What happens when the record being saved is identified as a possible duplicate depends on what’s defined in the duplicate rule (3).
For example, the duplicate rule could block users from saving the possible duplicate record or allow them to save it anyway.
Both the Block and Allow options include an alert, which tells users why they can’t save the record and what they need to do.
The Allow option includes the ability to report on the duplicate records.
When a user attempts to save an edited record, the record is first checked to see if the user has changed the value of a matching rule field.
If so, the duplicate management process works as described for new records.
If not, no further action is taken and duplicates are not detected.
Follow below steps to create matching and duplicate rule in salesforce
STEP 1 :
Go to setup>Administration Setup>Data.com Administration>Duplicate Management>Matching Rules
STEP 2 :
New Rule>SelectObject>
1. Rule Name : TestMatchingRule
2. Matching Rule Criteria : Select fileds which you want to match duplicate records
EX: Name : Exact
STEP 3 :
Go to setup>Administration Setup>Data.com Administration>Duplicate Management>Duplicate Rules
New Rule>Select Object>
In duplicate management give any name in name section
In Action section select action when duplicate rule has to fire
In Matching rule section select the matching rule before created
Condition section is optional
Click on save
Note : After saving duplicate or matching rule Activate the Matching as well as Duplicate rule
STEP 4 :
Go to object and try to create same record two times
Note : No need of Data.com Licence , it is free for all licence
That's all folk
