Is there a way to access the "previous row" value in a SELECT statement?
SQL has no built in notion of order, so you need to order by some column for this to be meaningful. Something like this:
select t1.value - t2.value from table t1, table t2
where t1.primaryKey = t2.primaryKey - 1
If you know how to order things but not how to get the previous value given the current one (EG, you want to order alphabetically) then I don't know of a way to do that in standard SQL, but most SQL implementations will have extensions to do it.
Here is a way for SQL server that works if you can order rows such that each one is distinct:
select rank() OVER (ORDER BY id) as 'Rank', value into temp1 from t
select t1.value - t2.value from temp1 t1, temp1 t2
where t1.Rank = t2.Rank - 1
drop table temp1
If you need to break ties, you can add as many columns as necessary to the ORDER BY.
How to get previous row value
You would have to join the table with itself, I'm not sure if this is 100% legitimate SQL, but I have no SQL-Server to try this at the moment, but try this:
SELECT (ID, Value) from table as table1
inner join table as table2
on table1.ID = (table2.ID -1)
How to get previous row data in sql server
Use lag()
function
select *, lag(col3) over (partition by col1 order by col2) as col4
from table t;
However You can also use subquery
if your SQL
doesn't have LAG()
select *,
(select top 1 col3
from table
where col1 = t.col1 and col2 < t.col2
order by col2 desc
) as col4
from table t;
Get previous row value based on a timestamp for matching IDs
You need to PARTITION BY
the ID
column.
lag(pc.CountryArrival) over (PARTITION BY ID order by DateArrival) as DeparturePort
Calculating a value in SQL using previous row's values and current row value
The structure seems odd to me.
But you can use the window function sum() over()
Declare @YourTable Table ([Type] varchar(50),[Current Value] int,[Transaction] int,[Date of transaction] date)
Insert Into @YourTable Values
('A',5,2,'12/31/2001')
,('A',5,-3,'12/30/2001')
,('A',5,-1,'12/29/2001')
,('A',5,6,'12/28/2001')
,('B',100,20,'12/31/2001')
,('B',100,-50,'12/30/2001')
,('B',100,-10,'12/29/2001')
,('B',100,30,'12/28/2001')
,('C',20,7,'12/31/2001')
,('C',20,-3,'12/30/2001')
Select *
,[Value at date] = [Current Value]
+ sum([Transaction]) over (partition by [Type] order by [Date of transaction] desc)
from @YourTable
Results
How to get previous row value in present row in sql server
you can use String_agg function like below
create table t (id int, name nvarchar(max));
insert into t values (1 , 'abc'),(2, 'def'),(3,'xyz');
select t1.id,string_agg(t2.name,'') from t t1 left join t t2
on t1.id>=t2.id
group by t1.id
demo link
How to Update a record Based on the the values on Previous row and Next Row
You could utilise lag
& lead
here and an updatable CTE:
with n as (
select *,
Lag(number) over(partition by UserId order by [Complete date]) pn,
Lead(number) over(partition by UserId order by [Complete date]) nn
from t
)
update n set number = pn
from n
where pn = nn and number is null;
See Demo Fiddle
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