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Exercise

COUNTing Data

Besides selecting one or more columns, limiting your results or just selecting distinct data, you might also want to get some summary of your data. This is handy in cases where you need to know, for example, the number of people that would be interested in getting to see a certain advertisement.

COUNT(*) can help you out here: it tells you how many rows are in a table.

However, if you want to count the number of non-missing values in a particular column, you can call COUNT on just that column.

Take a look at the following example, where you count the number of records that are present in the clients table:

SELECT COUNT(*)
FROM clients;

Now it's your turn!

Instructions

100 XP

Count the number of non-missing values in the education column.