Postgres window function using group and lag and other possible ways
Assume I have the table below and I would like to return only those rows where Price != price in the previous row but only within a group where the grouping is by Time
ID : { 1 , 2 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:00, 09:20:01, 09:20:02, 09:20:03 }
Price : { 100 , 100 , 101 , 102 , 102 , 103 }
Because of the grouping by time, the output returned should be:
ID : { 1 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:01, 09:20:02 , 09:20:03 }
Price : { 100 , 101 , 102 , 102 , 103 }
Do notice that the output discards one of the 100 price at 09:20 but does not discard 102 price at 09:20:02 even though it is same as price at 09:20:01 since the grouping has to be done by time. Can someone help me with a postgres query for something like this.
postgresql group-by lag
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
add a comment |
Assume I have the table below and I would like to return only those rows where Price != price in the previous row but only within a group where the grouping is by Time
ID : { 1 , 2 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:00, 09:20:01, 09:20:02, 09:20:03 }
Price : { 100 , 100 , 101 , 102 , 102 , 103 }
Because of the grouping by time, the output returned should be:
ID : { 1 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:01, 09:20:02 , 09:20:03 }
Price : { 100 , 101 , 102 , 102 , 103 }
Do notice that the output discards one of the 100 price at 09:20 but does not discard 102 price at 09:20:02 even though it is same as price at 09:20:01 since the grouping has to be done by time. Can someone help me with a postgres query for something like this.
postgresql group-by lag
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54
add a comment |
Assume I have the table below and I would like to return only those rows where Price != price in the previous row but only within a group where the grouping is by Time
ID : { 1 , 2 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:00, 09:20:01, 09:20:02, 09:20:03 }
Price : { 100 , 100 , 101 , 102 , 102 , 103 }
Because of the grouping by time, the output returned should be:
ID : { 1 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:01, 09:20:02 , 09:20:03 }
Price : { 100 , 101 , 102 , 102 , 103 }
Do notice that the output discards one of the 100 price at 09:20 but does not discard 102 price at 09:20:02 even though it is same as price at 09:20:01 since the grouping has to be done by time. Can someone help me with a postgres query for something like this.
postgresql group-by lag
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
Assume I have the table below and I would like to return only those rows where Price != price in the previous row but only within a group where the grouping is by Time
ID : { 1 , 2 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:00, 09:20:01, 09:20:02, 09:20:03 }
Price : { 100 , 100 , 101 , 102 , 102 , 103 }
Because of the grouping by time, the output returned should be:
ID : { 1 , 3 , 4 , 5 , 6 }
Time : { 09:20:00, 09:20:00, 09:20:01, 09:20:02 , 09:20:03 }
Price : { 100 , 101 , 102 , 102 , 103 }
Do notice that the output discards one of the 100 price at 09:20 but does not discard 102 price at 09:20:02 even though it is same as price at 09:20:01 since the grouping has to be done by time. Can someone help me with a postgres query for something like this.
postgresql group-by lag
postgresql group-by lag
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
edited Nov 15 '18 at 18:57
aajkaltak
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
asked Nov 15 '18 at 18:43
aajkaltakaajkaltak
47231026
47231026
How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54
add a comment |
How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54
How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54
add a comment |
1 Answer
1
active
oldest
votes
SELECT time, price
FROM mytable
WHERE price <> coalesce(
lag(price) OVER (PARTITION BY time ORDER BY id),
price - 1
)
ORDER BY time, id;
The coalesce takes care of the NULL value that appears for the first element in each partition.
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
SELECT time, price
FROM mytable
WHERE price <> coalesce(
lag(price) OVER (PARTITION BY time ORDER BY id),
price - 1
)
ORDER BY time, id;
The coalesce takes care of the NULL value that appears for the first element in each partition.
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
add a comment |
SELECT time, price
FROM mytable
WHERE price <> coalesce(
lag(price) OVER (PARTITION BY time ORDER BY id),
price - 1
)
ORDER BY time, id;
The coalesce takes care of the NULL value that appears for the first element in each partition.
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
add a comment |
SELECT time, price
FROM mytable
WHERE price <> coalesce(
lag(price) OVER (PARTITION BY time ORDER BY id),
price - 1
)
ORDER BY time, id;
The coalesce takes care of the NULL value that appears for the first element in each partition.
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
SELECT time, price
FROM mytable
WHERE price <> coalesce(
lag(price) OVER (PARTITION BY time ORDER BY id),
price - 1
)
ORDER BY time, id;
The coalesce takes care of the NULL value that appears for the first element in each partition.
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
answered Nov 15 '18 at 19:00
Laurenz AlbeLaurenz Albe
50.3k102950
50.3k102950
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
add a comment |
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
thank you! that worked
– aajkaltak
Nov 15 '18 at 19:21
add a comment |
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How is the order within a group defined?
– Laurenz Albe
Nov 15 '18 at 18:50
There is a unique id for every row, basically 3 columns ID, Time and Price. I have edited the table structure above.
– aajkaltak
Nov 15 '18 at 18:54