combine tables with 1 to N relationship into 1 line of record with the last value of the N record

问题

I need a modification of my previous post regarding how to combine tables with 1 to many relationship into 1 line of record

how to combine tables with 1 to many relationship into 1 line of record

now my problem is my record has now 1 to many relationship. What I need to show is the last record only and combine it in a single line tables tbl_equipment and tbl_warranty

and here is the desired output

here is the code I'm trying to implement

 SELECT
 a.equipmentid,
 a.codename,
 a.name,
 a.labelid,
 a.ACQUISITIONDATE,
 a.description,
 a.partofid,
 w1.warrantyid as serviceidwarranty,
 w1.startdate,
 w1.enddate,
 w2.warrantyid as productidwarranty,
 w2.startdate,
 w2.enddate,
 s.equipstatusid,
 l.equiplocationid FROM TBL_EQUIPMENTMST a
 left JOIN tbl_equipwarranty w1
 ON w1.equipmentid=a.equipmentid and w1.serviceproduct = 'service'
 left JOIN tbl_equipwarranty w2
 ON w2.equipmentid=a.equipmentid and w2.serviceproduct = 'product'
 left join tbl_equipstatus s
 on a.equipmentid = s.equipmentid
 left join tbl_equiplocation l
 on a.equipmentid = l.equipmentid  WHERE a.equipmentid = '112'

I only want to show 1 record with the last value of warranty product and warranty service in the output. Can anyone guide me how to modify my code so that when I try join all the tables listed above can produce 1 record only with the last record of warranty as an output. I am using firebird as a database. If you have a solution in mysql kindly tell me and ill try to find the counterpart in firebird.

回答1:

with summary as(
select e.equipmentid ,e.Codename,e.Name,w.warrantyid ,w.Satartdate ,w.Enddate,w.warrantytype 
from Eqp e
join Warranty w
on(w.equipmentid =e.equipmentid )
where w.warrantyid =3)

select *,w.warrantyid,w.Satartdate ,w.Enddate,w.warrantytype
from summary s
join  Warranty w
on s.Satartdate =w.Satartdate and s.Enddate =w.Enddate 
where w.warrantyid =4

回答2:

after reading the comment of Barmar at the question for solution. I Figured out subquery can solve my problem. Subquery is a new word for me. I research on how to use subquery and came out with a solution below. you can correct me if my code is wrong or how to improve the performance of the query

SELECT 
    a.equipmentid,a.codename,a.name,a.labelid,a.ACQUISITIONDATE,a.description,a.partofid,
    w1.warrantyid as serviceidwarranty,w1.startdate,w1.enddate,
    w2.warrantyid as productidwarranty,w2.startdate,w2.enddate,
    s.equipstatusid,
    l.equiplocationid 
FROM 
    TBL_EQUIPMENTMST a
left JOIN
    (select first 1 *
     from tbl_equipwarranty 
     where equipmentid='112' and serviceproduct = 'service'
     order by warrantyid desc) w1 ON w1.equipmentid = a.equipmentid 
                                     and w1.serviceproduct = 'service'
left JOIN
    (select first 1 *
     from tbl_equipwarranty 
     where equipmentid = '112' and serviceproduct = 'product'
     order by warrantyid desc) w2 ON w2.equipmentid = a.equipmentid 
                                     and w2.serviceproduct = 'product'
left join
    (select first 1 *
     from tbl_equipstatus 
     where equipmentid = '112'
     order by equipstatusid desc) s on a.equipmentid = s.equipmentid
left join
    (select first 1 *
     from tbl_equiplocation 
     where equipmentid = '112'
     order by equiplocationid desc) l on a.equipmentid = l.equipmentid  
WHERE 
     a.equipmentid = '112'

来源：https://stackoverflow.com/questions/26882396/combine-tables-with-1-to-n-relationship-into-1-line-of-record-with-the-last-valu

标签

mysql

sql

firebird

firebird2.5