I’m studying to interview for a job involving a lot of SQL. I’ve noticed a few exercises that revolve around returning values based on a sequence across rows, and I would love to know if there’s a standard way of doing this. Something akin to the subquery below I’ve found useful for selecting a max/min value: Here’s a relevant example
Tag: gaps-and-islands
SQl Query to get an output that resembles the image [closed]
I would like to get output the way its shown in the image attached and the way the input is organized is also shown in the image attached. Thanks!
How to get a continuous group of id
I’d like to increment an id by group, for each variation of an attribute with only 2 values. like this : result wanted I tried dense_rank() with window function but i only gives me 1 or 2 in grp column Answer You can use window functions to solve this gaps and islands problem. Her is an approch using lag() and
SQL Getting row number only when the value is different from all previous values
I want the count adding one only when the value has not been show before. The base table is: The goal is: I am thinking to compare the current row with all previous rows, but I have difficulty to call all previous rows. Thank you! Answer Several different ways to accomplish this. I guess you’ll get to pick one you
How to group data if difference between rows is mothe than 1 minute
Im trying to create a new table on SQL which will have summarized data. For example. In the original table i have this data: If you see rows 9, 10 and 11 they are consecutive, so i want to group them …
Rank based on cumulative value
I want to rank on ID and value columns based on ascending order of UID. Expected output has to change once value column has a different value than the previous value. Ranks has to restart on each new ID Here is a sample dataset that I have created: Answer I think that the simplest approach to this gaps-and-islands problem is
SQL Group by date with multiple same results
How to write a statement that groups data by date but shows when data changed for the first time date – when data changed a,b,c – some data and it can be anything This is should be the result. It might have the same data on different dates, but it missing the next day when data stayed the same. It
Making groups of dates in SQL Server
I have a table contains ids and dates, I want to groups of dates for each id id date —————— 1 2019-01-01 2 2019-01-01 1 2019-01-02 2 2019-01-02 2 …
SQL clean History repeated intermediate values
I’ve noticed that my table has multiple redundant values that should be cleaned, it’s a table that records price changes, so I would like to clean the following way: To this: Also assume that in this case the column id is the same as date. SELECT DISTINCT ON (product, price) won’t work because it would ignore either the product 1
Need to group records by consecutive date SQL
I’m building a query in order to build consecutive dates which is create table #consecutivedates ( sgid nvarchar(max), metric nvarchar(max), targetvalue nvarchar(max), startdate …