I have a table containing records of machine movements between multiple locations.
As I only show the latest of them in a list, i have read only the data rows with the latest record date per machine until now in sql.
Select *
From records
INNER JOIN
(Select max(processdate) as maxDate, machinetag, machineno
from records
group by machinetag, machineno ) as lrcd
on records.machineTag = lrcd.machineTag and records.machineno = lrcd.machineno
and records.processDate = lrcd.maxDate
I have read many posts but I did not find any solution.
How can I implement this scenario with queryover?
Thany you very much in advance.
Sascha
Inner joins can almost always be rewritten as a combination of a where clauses and projections.
Something like this (I'm writing without a compiler, sorry if there are any mistakes):
Select
records.*,
(select max(processdate) as maxdate
from records
where lrcd.machineno = records.machineno)
-- add more projections if you need them
From records
where records.processDate =
(select max(processdate) as maxDate
from records
where lrcd.machineno = records.machineno) as lrcd
This should be easy to implement with QueryOver now (subqueries can be implemented in projections or restrictions).
Don't worry about the duplicated code - the query plan will optimise it for you.
Now I can offer a (probably) working solution:
Dim r As Record = Nothing
Dim subquery = QueryOver.Of(Of Record)() _
.Where(Function(rec) rec.R_MachineTag = r.R_MachineTag) _
.And(Function(rec) rec.R_MachineNo = r.R_MachineNo) _
.Select(Projections.Max(Of Record)(Function(rec) rec.R_ProcessDate)).Take(1)
Dim query = session.QueryOver(Function() r) _
.WithSubquery.WhereProperty(Function(rec) rec.R_ProcessDate).Eq(subquery) _
.List()
Thanks to cbp for giving me the hint ;)
This statement represents my statement without inner joins:
Select r.*
from records as r
where r.processDate =
(Select max(processdate) as maxDate
from records as lr
where lr.machinetag = r.machinetag and
lr.machineno = r.machineno)
Related
My title is probably not very clear, so I made a little schema to explain what I'm trying to achieve. The xxxx_uid labels are foreign keys linking two tables.
Goal: Retrieve a column from the grids table by giving a proj_uid value.
I'm not very good with SQL joins and I don't know how to build a single query that will achieve that.
Actually, I'm doing 3 queries to perform the operation:
1) This gives me a res_uid to work with:
select res_uid from results where results.proj_uid = VALUE order by res_uid asc limit 1"
2) This gives me a rec_uid to work with:
select rec_uid from receptor_results
inner join results on results.res_uid = receptor_results.res_uid
where receptor_results.res_uid = res_uid_VALUE order by rec_uid asc limit 1
3) Get the grid column I want from the grids table:
select grid_name from grids
inner join receptors on receptors.grid_uid = grids.grid_uid
where receptors.rec_uid = rec_uid_VALUE;
Is it possible to perform a single SQL that will give me the same results the 3 I'm actually doing ?
You're not limited to one JOIN in a query:
select grids.grid_name
from grids
inner join receptors
on receptors.grid_uid = grids.grid_uid
inner join receptor_results
on receptor_results.rec_uid = receptors.rec_uid
inner join results
on results.res_uid = receptor_results.res_uid
where results.proj_uid = VALUE;
select g.grid_name
from results r
join resceptor_results rr on r.res_uid = rr.res_uid
join receptors rec on rec.rec_uid = rr.rec_uid
join grids g on g.grid_uid = rec.grid_uid
where r.proj_uid = VALUE
a small note about names, typically in sql the table is named for a single item not the group. thus "result" not "results" and "receptor" not "receptors" etc. As you work with sql this will make sense and names like you have will seem strange. Also, one less character to type!
I have a problem to join thoses 4 tables
Model of my database
I want to count the number of reservations with different sorts (user [mrbs_users.id], room [mrbs_room.room_id], area [mrbs_area.area_id]).
Howewer when I execute this query (for the user (id=1) )
SELECT count(*)
FROM mrbs_users JOIN mrbs_entry ON mrbs_users.name=mrbs_entry.create_by
JOIN mrbs_room ON mrbs_entry.room_id = mrbs_room.id
JOIN mrbs_area ON mrbs_room.area_id = mrbs_area.id
WHERE mrbs_entry.start_time BETWEEN "145811700" and "1463985000"
or
mrbs_entry.end_time BETWEEN "1458120600" and "1463992200" and mrbs_users.id = 1
The result is the total number of reservations of every user, not just the user who has the id = 1.
So if anyone could help me.. Thanks in advance.
Use parentheses in the where clause whenever you have more than one condition. Your where is parsed as:
WHERE (mrbs_entry.start_time BETWEEN "145811700" and "1463985000" ) or
(mrbs_entry.end_time BETWEEN "1458120600" and "1463992200" and
mrbs_users.id = 1
)
Presumably, you intend:
WHERE (mrbs_entry.start_time BETWEEN 145811700 and 1463985000 or
mrbs_entry.end_time BETWEEN 1458120600 and 1463992200
) and
mrbs_users.id = 1
Also, I removed the quotes around the string constants. It is bad practice to mix data types, and in some databases, the conversion between types can make the query less efficient.
The problem you've faced caused by the incorrect condition WHERE.
So, should be:
WHERE (mrbs_entry.start_time BETWEEN 145811700 AND 1463985000 )
OR
(mrbs_entry.end_time BETWEEN 1458120600 AND 1463992200 AND mrbs_users.id = 1)
Moreover, when you use only INNER JOIN (JOIN) then it be better to avoid WHERE clause, because the ON clause is executed before the WHERE clause, so criteria there would perform faster.
Your query in this case should be like this:
SELECT COUNT(*)
FROM mrbs_users
JOIN mrbs_entry ON mrbs_users.name=mrbs_entry.create_by
JOIN mrbs_room ON mrbs_entry.room_id = mrbs_room.id
AND
(mrbs_entry.start_time BETWEEN 145811700 AND 1463985000
OR ( mrbs_entry.end_time BETWEEN 1458120600 AND 1463992200 AND mrbs_users.id = 1)
)
JOIN mrbs_area ON mrbs_room.area_id = mrbs_area.id
This SQL is beyond my expertise. I think it should be fairly easy for someone with experience. Here is what I have so far..
SQL is as follows:
UPDATE (Tbl_Stg_Project_Schedule_Dates
INNER JOIN Tbl_Child_ITN ON Tbl_Stg_Project_Schedule_Dates.ms_itn = Tbl_Child_ITN.ITN)
INNER JOIN Tbl_Schedule ON Tbl_Child_ITN.Id = Tbl_Schedule.ID SET Tbl_Schedule.a_construction_start = [Tbl_Stg_Project_Schedule_Dates].[ms_start_date]
WHERE (((Tbl_Stg_Project_Schedule_Dates.ms_tempt_id) In (16,17,18,19,20,21,22,23)));
I want to add one last condition to this being that I only want the minimum of [Tbl_Stg_Project_Schedule_Dates].[ms_start_date] to update the table. I've tried the obvious of wrapping the field in Min, and also tried creating a separate aggregate select statement first (to get the min value with other criteria) that I then tried to create the update query from in new query but no luck.
I believe this is valid Access/Jet SQL. The idea here is to use a subquery to look up the earliest date among all the rows in your subset. I'm not sure if ms_itn was the right column to correlate on but hopefully you get the idea:
UPDATE (Tbl_Stg_Project_Schedule_Dates
INNER JOIN Tbl_Child_ITN ON Tbl_Stg_Project_Schedule_Dates.ms_itn = Tbl_Child_ITN.ITN)
INNER JOIN Tbl_Schedule ON Tbl_Child_ITN.Id = Tbl_Schedule.ID
SET Tbl_Schedule.a_construction_start = [Tbl_Stg_Project_Schedule_Dates].[ms_start_date]
WHERE (((Tbl_Stg_Project_Schedule_Dates.ms_tempt_id) In (16,17,18,19,20,21,22,23)))
and [Tbl_Stg_Project_Schedule_Dates].[ms_start_date] = (
select min(sd.[ms_start_date])
from [Tbl_Stg_Project_Schedule_Dates] as sd
where sd.ms_itn = [Tbl_Stg_Project_Schedule_Dates].ms_itn
)
I have a DB2 query as follows:
SELECT DISTINCT RETAILMASTERFILE.DOIDCD AS "RETAILMASTERFILE_DOIDCD",
RETAILMASTERFILE.COCOMO AS "RETAILMASTERFILE_COCOMO",
#XENOS.CUSTREF AS "XENOS_CUSTREF",
#XENOS.ADDUDT AS "XENOS_ADDUDT",
#XENOS.ADUPDD AS "XENOS_ADUPDD",
#XENOS.ADUPDT AS "XENOS_ADUPDT",
#XENOS.ADSTAT AS "XENOS_ADSTAT"
FROM RETAILMASTERFILE INNER JOIN
#XENOS ON RETAILMASTERFILE.DOCOMP = #XENOS.ADCOMP
AND RETAILMASTERFILE.COCOMO = #XENOS.ADDELN
WHERE (RETAILMASTERFILE.DOIDCD = 'CUST008')
AND (RETAILMASTERFILE.COCOMO = '345126032')
AND (RETAILMASTERFILE.DOCOMP = 'LONDON')
The problem is #XENOS.ADUPDT may not be unique which gives me an unwanted duplicate record.
Is there any way I can exclude this from consideration ? Everything I've tried so far within my limited knowledge and crude understanding of group by has so far broken my query.
Use GROUP BY instead:
SELECT RETAILMASTERFILE.DOIDCD AS "RETAILMASTERFILE_DOIDCD",
RETAILMASTERFILE.COCOMO AS "RETAILMASTERFILE_COCOMO",
#XENOS.CUSTREF AS "XENOS_CUSTREF",
#XENOS.ADDUDT AS "XENOS_ADDUDT",
#XENOS.ADUPDD AS "XENOS_ADUPDD",
MAX(#XENOS.ADUPDT) AS "XENOS_ADUPDT",
#XENOS.ADSTAT AS "XENOS_ADSTAT"
FROM RETAILMASTERFILE INNER JOIN
#XENOS
ON RETAILMASTERFILE.DOCOMP = #XENOS.ADCOMP AND
RETAILMASTERFILE.COCOMO = #XENOS.ADDELN
WHERE (RETAILMASTERFILE.DOIDCD = 'CUST008') AND (RETAILMASTERFILE.COCOMO = '345126032') AND
(RETAILMASTERFILE.DOCOMP = 'LONDON')
GROUP BY RETAILMASTERFILE.DOIDCD,
RETAILMASTERFILE.COCOMO,
#XENOS.CUSTREF,
#XENOS.ADDUDT,
#XENOS.ADUPDD,
#XENOS.ADSTAT;
Here is the situation:
I search for Persons with ID (empr.empr_cb)
that has bill(s) to pay (transactions.montant)
this refers to transactions.compte_id
which is identical to comptes.id_compte
this refers to comptes.proprio.id
which is identical to empr.id_empr
that would give us the Person ID (empr.empr_cb)
I tried this, but I don't know what joins to set (cross Join?):
SELECT `empr`.`empr_cb`,`transactions`.`montant`
FROM `empr`,`comptes`,`transactions`
WHERE `transactions`.`montant` > `0`
AND `transactions`.`encaissement` = `0`
AND `transactions`.compte_id` = `comptes`.`id_compte`
AND `comptes`.`proprio_id` = `id_empr`
Any ideas how to put the joins?
This query is already using implicit INNER JOINs. It can be rewritten this way:
SELECT empr.empr_cb
, transactions.montant
FROM empr
JOIN comptes ON comptes.proprio_id = empr.id_empr
JOIN transactions ON transactions.compte_id = comptes.id_compte
WHERE transactions.encaissement = 0
AND transactions.montant > 0