Create Attribute of Comma Seperated Values [duplicate]

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I have a loans dataset and each row represents a loan plan and has a customer ID associated with it.

Loan_ID    Customer_ID    
1          A            
2          B           
3          A           
4          C 
5          A
6          C     

I want to create a seperate table which will be grouped by Customer_ID and will contain an attribute that is a comma seperated list of the Loan_ID.

Customer_ID    Loan_ID_List
A              1,3,5
B              2
C              4,6