Oracle / SQL - Count number of occurrences of values in a single column
Use:
SELECT t.code, COUNT(*) AS numInstances FROM YOUR_TABLE tGROUP BY t.codeThe output will resemble:
code numInstances--------------------A 3B 5C 1If a code exists that has not been used, it will not show up. You'd need to LEFT JOIN to the table containing the list of codes in order to see those that don't have any references.