18.3. Filtering with Aggregated Results

If we want to answer the question “Which stations were the starting point for 10,000 or more rides?”, it would seem like we want to write something like this:

  COUNT(*) AS n_trips
  n_trips > 10000

Unfortunately, you can never include an aggregating function or result within the WHERE clause. Trying to do so will give an error. However, there is a HAVING clause that can be used just like a WHERE to filter data, only it works with aggregations. To ask about the stations with over 10000 trips we would write:

As with the ORDER BY clause, HAVING is an operation on the results. While WHERE filters the data being queried, HAVING filters the results based on the value of an aggregating function. The HAVING clause can only be used immediately following the GROUP BY clause.

Below is a query to find the total time each bike was ridden. Add a HAVING clause to select only the bikes that were used for less than 1000 minutes.

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