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SQL Basics

bookHow many unique?

But what if we want to calculate the number of unique site visitors? Sounds like a combination of selecting unique and then counting...

Yes, that's the point! To calculate the number of unique observations over a certain column use COUNT(DISTINCT( ... )) statement. For example,


              
12

            
SELECT COUNT(DISTINCT(user_id))
FROM visitors
copy

This query will return a single value - the number of unique user_id in the visitors table.

Task

Swipe to start coding

Count the number of different cars models in the audi_cars table.

Solution

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SectionΒ 1. ChapterΒ 7
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bookHow many unique?

Swipe to show menu

But what if we want to calculate the number of unique site visitors? Sounds like a combination of selecting unique and then counting...

Yes, that's the point! To calculate the number of unique observations over a certain column use COUNT(DISTINCT( ... )) statement. For example,


              
12

            
SELECT COUNT(DISTINCT(user_id))
FROM visitors
copy

This query will return a single value - the number of unique user_id in the visitors table.

Task

Swipe to start coding

Count the number of different cars models in the audi_cars table.

Solution

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

SectionΒ 1. ChapterΒ 7
single

single

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