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42 строки
1.3 KiB
Plaintext
42 строки
1.3 KiB
Plaintext
partition
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https://edu.postgrespro.ru/sqlprimer/sqlprimer-2019-msu-04.pdf
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! p68
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select
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...
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count(*) over (
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partition by date_trunc('month', b.book_date)
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order by b.book_date
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) as count
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from
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...
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join bookings b on ...
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;
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over - necessary keyword (count function became a window-one)
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! p76
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first_value
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??? WINDOW - to name over-conditions (https://habr.com/ru/post/268983/)
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row_number
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rank
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lag
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lead
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first_value, last_value, nth_value
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- aggregates like sum, count
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sample
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select depname, empno, salary, avg(salary) over (partition by depname) from empsalary;
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depname | empno | salary | avg
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-----------+-------+--------+-----------------------
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develop | 11 | 5200 | 5020.0000000000000000
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develop | 7 | 4200 | 5020.0000000000000000
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develop | 9 | 4500 | 5020.0000000000000000
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develop | 8 | 6000 | 5020.0000000000000000
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develop | 10 | 5200 | 5020.0000000000000000
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personnel | 5 | 3500 | 3700.0000000000000000
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personnel | 2 | 3900 | 3700.0000000000000000
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sales | 3 | 4800 | 4866.6666666666666667
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sales | 1 | 5000 | 4866.6666666666666667
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sales | 4 | 4800 | 4866.6666666666666667
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(10 rows)
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