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Exercise

Extracting hours from a time value

Your team has been tasked with generating a summary report to better understand the hour of the day when most parking violations are occurring. The violation_time field has been imported into the database using strings consisting of the hour (in 12-hour format), the minutes, and AM/PM designation for each violation. An example time stored in this field is '1225AM'. Note the lack of a colon and space in this format.

Use the TO_TIMESTAMP() function and the proper format string to convert the violation_time into a TIMESTAMP, extract the hour from the TIME component of this TIMESTAMP, and provide a count of all parking violations by hour issued. The given conversion to a TIME value is performed because violation_time values do not include date information.

Instructions 1/2

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  • Convert violation_time to a TIMESTAMP using the TO_TIMESTAMP() function and a format string including 12-hour format (HH12), minutes (MI), and meridian indicator (AM or PM). ::TIME converts the resulting timestamp value to a TIME.
  • Exclude records with a NULL-valued violation_time.