I work on sql server 2012 I don't understand condition below do this condition as below case WHEN Po.PortionKey LIKE '%[_]%' THEN SUBSTRING(Po.PortionKey, LEN(LTRIM(RTRIM(Po.PortionKey)))+1,LEN(LTRIM(RTRIM(Po.PortionKey)))) end as modifiedportionkey what condition above mean can please give me sample