Exercise: Set importance column according to no of places

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The answer to the exercise will be included and explained if you attend the Wise Owl course listed below!

Category ==> SQL  (115 exercises)
Topic ==> Transactions  (4 exercises)
Level ==> Harder than average
Course ==> Advanced SQL
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help).

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If you haven't already done so, run the stored procedure in the above folder to generate a database of training courses and delegates.

Add a new integer column called Importance to the tblPerson table:

SQL exercise - Transactions (image 1)

The new column

Write a query which begins a transaction, and then updates the value of the Importance column for each person to:

  • 10 if this person has attended 1 or less courses (ie if the number of rows in the tblDelegate table for this PersonId is less than or equal to 1)
  • 20 if this person has attended 2 to 4 courses; or
  • 30 otherwise

Extend this query so that it deletes all "unimportant" people (ie those whose importance is 10), and prints out a message saying how many rows have been deleted:

SQL exercise - Transactions (image 2)

You should see 274 people have been zapped

Finally, add a condition which:

  • commits the transaction if there are still at least 500 people left in the table; or
  • rolls it back otherwise

Optionally, save this query as How not to run a training company.sql, then close it down.

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