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  3. Exploratory Data Analysis in SQL

Exercise

Count missing values

Which column of fortune500 has the most missing values? To find out, you'll need to check each column individually, although here we'll check just three.

Course Note: While you're unlikely to encounter this issue during this exercise, note that if you run a query that takes more than a few seconds to execute, your session may expire or you may be disconnected from the server. You will not have this issue with any of the exercise solutions, so if your session expires or disconnects, there's an error with your query.

Instructions 1/4

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  • 1
    • First, figure out how many rows are in fortune500 by counting them.
  • 2
    • Subtract the count of the non-NULL ticker values from the total number of rows; alias the difference as missing.
  • 3
    • Repeat for the profits_change column.
  • 4
    • Repeat for the industry column.