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SQL Tutorial for Beginners

bookSQL Null

NULL is a special value that matches missed data. It means there is no data inserted into the field.

There are operators to detect whether the value is NULL:

  • IS NULL: detects only values that equal to NULL
  • IS NOT NULL: detects values that are not NULL.

              
12

            
SELECT title FROM songs
WHERE album IS NOT NULL
copy

NULL does not match 0 or empty line, it only matches data that is missing and does not exist.

NULL values are ignored in the MIN, MAX, COUNT, AVG, and SUM aggregate functions.

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Sezione 3. Capitolo 1
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NULL is a special value that matches missed data. It means there is no data inserted into the field.

There are operators to detect whether the value is NULL:

  • IS NULL: detects only values that equal to NULL
  • IS NOT NULL: detects values that are not NULL.

              
12

            
SELECT title FROM songs
WHERE album IS NOT NULL
copy

NULL does not match 0 or empty line, it only matches data that is missing and does not exist.

NULL values are ignored in the MIN, MAX, COUNT, AVG, and SUM aggregate functions.

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Tutto è chiaro?

Come possiamo migliorarlo?

Grazie per i tuoi commenti!

close

Awesome!

Completion rate improved to 4.17
Sezione 3. Capitolo 1
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