Hi I have a query which looks like the following :
SELECT device_id, tag_id, at, _deleted, data,
row_number() OVER (PARTITION BY device_id ORDER BY at DESC) AS row_num
FROM mdb_history.devices_tags_mapping_history
WHERE at <= '2019-04-01'
AND _deleted = False
AND (tag_id = '275674' or tag_id = '275673')
AND row_num = 1
However when I run the following query, I get the following error :
ERROR: column "row_num" does not exist
Is there any way to go about this. One way I tried was to use it in the following way:
SELECT * from (SELECT device_id, tag_id, at, _deleted, data,
row_number() OVER (PARTITION BY device_id ORDER BY at DESC) AS row_num
FROM mdb_history.devices_tags_mapping_history
WHERE at <= '2019-04-01'
AND _deleted = False
AND (tag_id = '275674' or tag_id = '275673')) tag_deleted
WHERE tag_deleted.row_num = 1
But this becomes way too complicated as I do it with other queries as I have number of join and I have to select the column as stated from so it causes alot of select statement. Any smart way of doing that in a more simpler way. Thanks
You can't refer to the row_num alias which you defined in the same level of the select in your query. So, your main option here would be to subquery, where row_num would be available. But, Postgres actually has an option to get what you want in another way. You could use DISTINCT ON here:
SELECT DISTINCT ON (device_id), device_id, tag_id, at, _deleted, data
FROM mdb_history.devices_tags_mapping_history
WHERE
at <= '2019-04-01' AND
_deleted = false AND
tag_id IN ('275674', '275673')
ORDER BY
device_id,
at DESC;
Too long/ formatted for a comment. There is a reason behind #TimBiegeleisen statement "alias which you defined in the same level of the select". That reason is that all SQL statement follow the same sequence for evaluation. Unfortunately that sequence does NOT follow the sequence of clauses within the statement presentation. that sequence is in order:
from
where
group by
having
select
limits
You will notice that what actually gets selected fall well after evaluation of the where clause. Since your alias is defined within the select phase it does not exist during the where phase.
Related
I have the following data structure and I want to write a query that returns for a given order number, all the orderlineid's with the most recent statusId for that orderline.
If I was just interested in a particular order line I could use
select top 1 StatusId from task where OrderLineId = #OrderLineId order by TaskId desc
but I can't figure out how to get all the results for a given OrderId in one SQL Statement.
If I'm understanding your question correctly, you could use row_number in a subquery:
select orderid, orderlineid, statusid
from (
select o.orderid,
ol.orderlineid,
t.statusid,
row_number() over (partition by o.orderid order by t.taskid desc) rn
from order o
join orderline ol on o.orderid = ol.orderid
join task t on ol.orderlineid = t.orderlineid
) t
where orderid = ? and rn = 1
Please note, order is a reserved word in sql server so if that's your real table name, you'll need to use brackets around it. But I'd recommend renaming it to make your life easier.
So far I have come up with the below:
WHERE (extract(month FROM orders)) =
(SELECT min(extract(month from orderdate))
FROM orders)
However, that will consequently return zero to many rows, and in my case, many, because many orders exist within that same earliest (minimum) month, i.e. 4th February, 9th February, 15th Feb, ...
I know that a WHERE clause can contain multiple columns, so why wouldn't the below work?
WHERE (extract(day FROM orderdate)), (extract(month FROM orderdate)) =
(SELECT min(extract(day from orderdate)), min(extract(month FROM orderdate))
FROM orders)
I simply get: SQL Error: ORA-00920: invalid relational operator
Any help would be great, thank you!
Sample data:
02-Feb-2012
14-Feb-2012
22-Dec-2012
09-Feb-2013
18-Jul-2013
01-Jan-2014
Output:
02-Feb-2012
14-Feb-2012
Desired output:
02-Feb-2012
I recreated your table and found out you just messed up the brackets a bit. The following works for me:
where
(extract(day from OrderDate),extract(month from OrderDate))
=
(select
min(extract(day from OrderDate)),
min(extract(month from OrderDate))
from orders
)
Use something like this:
with cte1 as (
select
extract(month from OrderDate) date_month,
extract(day from OrderDate) date_day,
OrderNo
from tablename
), cte2 as (
select min(date_month) min_date_month, min(date_day) min_date_day
from cte1
)
select cte1.*
from cte1
where (date_month, date_day) = (select min_date_month, min_date_day from cte2)
A common table expression enables you to restructure your data and then use this data to do your select. The first cte-block (cte1) selects the month and the day for each of your table rows. Cte2 then selects min(month) and min(date). The last select then combines both ctes to select all rows from cte1 that have the desired month and day.
There is probably a shorter solution to that, however I like common table expressions as they are almost all the time better to understand than the "optimal, shortest" query.
If that is really what you want, as bizarre as it seems, then as a different approach you could forget the extracts and the subquery against the table to get the minimums, and use an analytic approach instead:
select orderdate
from (
select o.*,
row_number() over (order by to_char(orderdate, 'MMDD')) as rn
from orders o
)
where rn = 1;
ORDERDATE
---------
01-JAN-14
The row_number() effectively adds a pseudo-column to every row in your original table, based on the month and day in the order date. The rn values are unique, so there will be one row marked as 1, which will be from the earliest day in the earliest month. If you have multiple orders with the same day/month, say 01-Jan-2013 and 01-Jan-2014, then you'll still only get exactly one with rn = 1, but which is picked is indeterminate. You'd need to add further order by conditions to make it deterministic, but I have no idea what you might want.
That is done in the inner query; the outer query then filters so that only the records marked with rn = 1 is returned; so you get exactly one row back from the overall query.
This also avoids the situation where the earliest day number is not in the earliest month number - say if you only had 01-Jan-2014 and 02-Feb-2014; comparing the day and month separately would look for 01-Feb-2014, which doesn't exist.
SQL Fiddle (with Thomas Tschernich's anwer thrown in too, giving the same result for this data).
To join the result against your invoice table, you don't need to join to the orders table again - especially not with a cross join, which is skewing your results. You can do the join (at least) two ways:
SELECT
o.orderno,
to_char(o.orderdate, 'DD-MM-YYYY'),
i.invno
FROM
(
SELECT o.*,
row_number() over (order by to_char(orderdate, 'MMDD')) as rn
FROM orders o
) o, invoices i
WHERE i.invno = o.invno
AND rn = 1;
Or:
SELECT
o.orderno,
to_char(o.orderdate, 'DD-MM-YYYY'),
i.invno
FROM
(
SELECT orderno, orderdate, invno
FROM
(
SELECT o.*,
row_number() over (order by to_char(orderdate, 'MMDD')) as rn
FROM orders o
)
WHERE rn = 1
) o, invoices i
WHERE i.invno = o.invno;
The first looks like it does more work but the execution plans are the same.
SQL Fiddle with your pastebin-supplied query that gets two rows back, and these two that get one.
I would like to do something like this:
CNT=2;
//[edit]
select avg(price) from (
select first :CNT p.Price
from Price p
order by p.Date desc
);
This does not work, Firebird does not allow :cnt as a parameter to FIRST. I need to average the first CNT newest prices. The number 2 changes so it can not be hard-coded.
This can be broken out into a FOR SELECT loop and break when a count is reached. Is that the best way though? Can this be done in a single SQL statement?
Creating the SQL as a string and running it is not the best fit either. It is important that the database compile my SQL statement.
You don't have to use CTE, you can do it directly:
select avg(price) from (
select first :cnt p.Price
from Price p
order by p.Date desc
);
You can use a CTE (Common Table Expression) (see http://www.firebirdsql.org/refdocs/langrefupd21-select.html#langrefupd21-select-cte) to select data before calculate average.
See example below:
with query1 as (
select first 2 p.Price
from Price p
order by p.Date desc
)
select avg(price) from query1
I have the following table
-----Account#----Period-----Balance
12345---------200901-----$11554
12345---------200902-----$4353
12345 --------201004-----$34
12345 --------201005-----$44
12345---------201006-----$1454
45677---------200901-----$14454
45677---------200902-----$1478
45677 --------201004-----$116776
45677 --------201005-----$996
56789---------201006-----$1567
56789---------200901-----$7894
56789---------200902-----$123
56789 --------201003-----$543345
56789 --------201005-----$114
56789---------201006-----$54
I want to select the account# that have a period of 201005.
This is fairly easy using the code below. The problem is that if a user enters 201003-which doesnt exist- I want the query to select the previous value.*NOTE that there is an account# that has a 201003 period and I still want to select it too.*
I tried CASE, IF ELSE, IN but I was unsuccessfull.
PS:I cannot create temp tables due to system limitations of 5000 rows.
Thank you.
DECLARE #INPUTPERIOD INT
#INPUTPERIOD ='201005'
SELECT ACCOUNT#, PERIOD , BALANCE
FROM TABLE1
WHERE PERIOD =#INPUTPERIOD
SELECT t.ACCOUNT#, t.PERIOD, t.BALANCE
FROM (SELECT ACCOUNT#, MAX(PERIOD) AS MaxPeriod
FROM TABLE1
WHERE PERIOD <= #INPUTPERIOD
GROUP BY ACCOUNT#) q
INNER JOIN TABLE1 t
ON q.ACCOUNT# = t.ACCOUNT#
AND q.MaxPeriod = t.PERIOD
select top 1 account#, period, balance
from table1
where period >= #inputperiod
; WITH Base AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY Period DESC) RN FROM #MyTable WHERE Period <= 201003
)
SELECT * FROM Base WHERE RN = 1
Using CTE and ROW_NUMBER() (we take all the rows with Period <= the selected date and we take the top one (the one with auto-generated ROW_NUMBER() = 1)
; WITH Base AS
(
SELECT *, 1 AS RN FROM #MyTable WHERE Period = 201003
)
, Alternative AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY Period DESC) RN FROM #MyTable WHERE NOT EXISTS(SELECT 1 FROM Base) AND Period < 201003
)
, Final AS
(
SELECT * FROM Base
UNION ALL
SELECT * FROM Alternative WHERE RN = 1
)
SELECT * FROM Final
This one is a lot more complex but does nearly the same thing. It is more "imperative like". It first tries to find a row with the exact Period, and if it doesn't exists does the same thing as before. At the end it unite the two result sets (one of the two is always empty). I would always use the first one, unless profiling showed me the SQL wasn't able to comprehend what I'm trying to do. Then I would try the second one.
I have the following Inline Table-Valued Function:
SELECT Locations.LocationId,
dbo.Search_GetSuitability(#SearchPreferences,
Score.FieldA, Score.FieldB, Score.FieldC) AS OverallSuitabilityScore,
RANK() OVER (ORDER BY OverallSuitabilityScore) AS OverallSuitabilityRank
FROM dbo.LocationsView Locations
INNER JOIN dbo.LocationScores Score ON Locations.LocationId = Score.LocationId
WHERE Locations.CityId = #LocationId
That RANK() line is giving me an error:
Invalid column name 'OverallSuitabilityScore'.
The function dbo.Search_GetSuitability is a scalar-function which returns a DECIMAL(8,5). I need to assign a rank to each row based on that value.
The only way i can get the above to work is to add the scalar function call in the ORDER BY part again - which is silly. I have about 5 of these scalar function calls and i need seperate RANK() values for each.
What can i do? Can i use a Common Table Expression (CTE) ?
Yep, you can't reference a column alias in the SELECT clause. The CTE sounds good though. Here's an example
WITH Score as
(
select Score.LocationId, Score.FieldA, Score.FieldB, Score.FieldC,
dbo.Search_GetSuitability(#SearchPreferences,
Score.FieldA, Score.FieldB, Score.FieldC) AS OverallSuitabilityScore
from dbo.LocationScores
)
SELECT TOP(10)
Locations.LocationId,
Score.OverallSuitabilityScore,
RANK() OVER (ORDER BY OverallSuitabilityScore) AS OverallSuitabilityRank
FROM dbo.LocationsView Locations
INNER JOIN Score ON Locations.LocationId = Score.LocationId
WHERE Locations.CityId = #LocationId
An old school way of doing this is just to SUBQUERY the expression.
The CTE here only moves the subquery to the top
SELECT TOP(10) LocationId,
OverallSuitabilityScore,
RANK() OVER (ORDER BY OverallSuitabilityScore) AS OverallSuitabilityRank
FROM
(
SELECT
Locations.LocationId,
dbo.Search_GetSuitability(#SearchPreferences,
Score.FieldA, Score.FieldB, Score.FieldC) AS OverallSuitabilityScore
FROM dbo.LocationsView Locations
INNER JOIN dbo.LocationScores Score ON Locations.LocationId = Score.LocationId
WHERE Locations.CityId = #LocationId
) X