Find the difference between the total number of CITY entries in the table and the number of distinct CITY entries in the table.
The STATION table is described as follows: SOLUTION: SELECT COUNT(CITY)-COUNT(DISTINCT CITY) FROM STATION; Explanation: COUNT(*) counts all rows (including duplicates and nulls in other columns, but not in CITY directly). COUNT(DISTINCT CITY) counts unique cities only . Subtracting the two gives you the number of duplicate city entries .