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Introduction
Multiple metrics for a single object
Metrics for two groups
Ratios and percentages
8. Calculating ratios – step 3
Global vs. specific metrics
Summary

Instruction

Good job! Even though we already computed the final ratio in step 2, we typically also want to round the ratio to a given number of decimal places. To that end, we can use the ROUND(value, decimal_places) function. Take a look:

SELECT
  COUNT(CASE
    WHEN shipped_date IS NOT NULL
      THEN order_id
  END) AS count_shipped,
  COUNT(order_id) AS count_all,
  ROUND(COUNT(CASE
    WHEN shipped_date IS NOT NULL
      THEN order_id
  END) / COUNT(order_id)::decimal, 2) AS shipped_ratio
FROM orders;

We surrounded the last column with the ROUND(..., 2) function invocation. Because the second argument is 2, we'll get the ratio rounded to two decimal places.

Exercise

Modify the template code. Round the ratio from the discounted_ratio column to three decimal places.

Stuck? Here's a hint!

Wrap your division with a call to ROUND(..., 3).