Clever Geek Handbook

How to use LEAD and LAG Where?

I have a table like this:

Number   Price    Type       Date         Time
------   -----    ----    ----------    ---------
23456    0,665     SV     2014/02/02     08:00:02
23457    1,3       EC     2014/02/02     07:50:45
23460    0,668     SV     2014/02/02     07:36:34
23461    0,668     SV     2014/02/02     07:37:34
23462    0,668     SV     2014/02/02     07:38:34
23463    0,668     SV     2014/02/02     07:39:34

For each entry, I need the previous / next price. In this case, the request is simple.

Select Lag(price) over (order by date desc, time desc),
Lead(price) over (order by date desc, time desc)
from ITEMS

but I need the result Where Next price <> record price

My request

    Select Lag(price) over (order by date desc, time desc) Nxt_Price,
    Lead(price) over (order by date desc, time desc) Prv_Price
    from ITEMS
 Where Nxt_Price <> price

but he refused to use this variable

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2 answers


Try the following query:

SELECT Nxt_Price, Prv_Price 
FROM
    (Select price, Lag(price) over (order by date desc, time desc) Nxt_Price,
    Lead(price) over (order by date desc, time desc) Prv_Price
    from ITEMS) AS InnerQuery
 Where Nxt_Price <> price


This might help you.

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Use a general table expression.



with myItems as (
     Select Lag(price) over (order by date desc, time desc) Nxt_Price,
    Lead(price) over (order by date desc, time desc) Prv_Price
    from ITEMS
)
select *
from myItems
where Nxt_Price <> Prv_Price
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