![]() Some of these queries are native PostgreSQL, and some are additional functions provided by. This is also true for the 3rd record which is the first record for the partition where the ‘extra_marks’ is 15 and the 5th record which is the first record for the partition where the ‘extra_marks’ is 20. You can use Timescale for a variety of analytical queries. For example, an offset of 1 returns the following row. The first record in the result set is the first record for the partition where ‘extra_marks’ is 10 and thus has a value of NULL for the ‘prev_marks’ as there is no lower ‘marks’ value in this partition. Lag: for an offset value n, the lag function returns the value that is n rows before the current row. ![]() The LAG function will restart its calculations, whenever a new ‘extra_marks’ is encountered. LAG (marks,1) OVER (PARTITION BY extra_marks ORDER BY marks) AS prev_marksĮxplanation: Here, the LAG function will sort all of the ‘marks’ in ascending order after the partition of the results by ‘extra_marks’ in the ‘students’ table and since we used an offset of 1, it will then return the previous marks. lag(value any, offset integer, default any ), same type as value, returns value evaluated at the row that is offset rows before the current row within. Need to emulate Oracle IGNORE NULLS in window functions (LEAD and LAG) in PostgreSQL. LAG (marks, 1 ) OVER (PARTITION BY extra_marks ORDER BY marks ) AS prev_marks
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