How can I get only the First Name of all the Customers from the Table using a Single Query?

Hello Experts,

There are few records in a table.

One of the column is FIRSTNAME_MIDDLENAME_LASTNAME.

Means it contains FirstName MiddleName(Those who have) and LastName for all the records.

EX:- Samir_Kumar_Roy
Rakesh_Ranjan_Dash
Vishal_Sharma
Ragini_Jain
Raj_Shekhar_Reddy
and so on.

And my query is that how can I get only the FirstName of all the customers from the table using a single query?

Please assist here.

Thanks in advance.