Crontab Format

                                                                    
*  *  * * * *                                                       
|    |   |  |  |  |                                                       
|    |   |  |  | +-- Year                      (range: 1900-3000)                
|    |   |  | +---- Day of the Week   (range: 1-7, 1 standing for Monday)
|    |   | +------ Month of the Year (range: 1-12)                     
|    |  +-------- Day of the Month  (range: 1-31)                     
|   +----------- Hour                     (range: 0-23)                      
+-------------- Minute                  (range: 0-59)      

Find duplicate rows in a table

select city_name
from areas
group by city_name
having count(*) > 1