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SQL Distinct
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Distinct is a keyword used with SELECT to return only unique values. Usually, you want to get all unique values, but there are duplicate values stored in the tables.
Check the difference: in our table, there are 18 records at all, and each record has a singer. You'll retrieve the 18 singers with the next query:
12SELECT singer FROM songs
But some singers, for example, AC/DC, occur multiple times. To retrieve the unique singers, use the DISTINCT keyword before the singer column:
12SELECT DISTINCT singer FROM songs
Now there are no repeated values, so you can see that the total number of unique singers is 10.
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Find all unique title values in songs.
Soluzione
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