Mysql: set existing column as Primary Key in MySQL

I have a database with 3 columns:

id, name, somethingelse  

This table has no index set and i am getting "No index defined!" in phpmyadmin
id is a 7digit alphanumeric value, unique to each row.
I want to set Drugid to be the primarykey/index (i dont know the difference if there is one)

 Answers

Either run in SQL:

ALTER TABLE tableName
  ADD PRIMARY KEY (id)           ---or Drugid, whichever you want it to be PK

or use the PHPMyAdmin interface (Table Structure)

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If you want to do it with phpmyadmin interface:

Select the table -> Go to structure tab -> On the row corresponding to the column you want, click on the icon with a key

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Go to localhost/phpmyadmin and press enter key. Now select database --> table_name --->Structure --->Action ---> Primary -->click on Primary