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SQL Statement for limiting the number of detail retrieved in Access 2000?Hello All,
How do I limit the number of detail records selected in a Master-Detail set using SQL? I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've been trying with "TOP 3", but can't get anywhere. Using Access 2000. Something like: SELECT t1.*, TOP 3 t2.* FROM t1, t2 WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) Any help appreciated, Hexman Try this: (Or something of the like)
SELECT t1.*, t3.* FROM t1 INNER JOIN (SELECT TOP 3 t2.* FROM t2) t3 ON t1.Item = t3.Item WHERE (t1.TrnDate = #09/23/06#) You may even want too use a LEFT OUTER JOIN for this, depends on your data. Izzy Hexman wrote: Show quoteHide quote > Hello All, > > How do I limit the number of detail records selected in a Master-Detail set using SQL? > > I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've > been trying with "TOP 3", but can't get anywhere. Using Access 2000. > > Something like: > > SELECT t1.*, TOP 3 t2.* > FROM t1, t2 > WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) > > Any help appreciated, > > Hexman Izzy,
Thanks for the response. I still can't get it to work, either with Access or SS EE. It generates no error during execution, but doesn't return any rows. If I take out the "(SELECT TOP 3 t2.* FROM t2)" and change all "t3" references to "t2", it retrieves the rows (except too many of them). This has me stumped. Any further ideas? All I want to do is limit the number of rows returned from t2 to be joined with t1. Thanks, Hexman Show quoteHide quote On 23 Sep 2006 16:17:22 -0700, "Izzy" <israel.rich***@gmail.com> wrote: >Try this: (Or something of the like) > >SELECT t1.*, t3.* >FROM t1 >INNER JOIN >(SELECT TOP 3 t2.* > FROM t2) t3 ON t1.Item = t3.Item >WHERE (t1.TrnDate = #09/23/06#) > >You may even want too use a LEFT OUTER JOIN for this, depends on your >data. > >Izzy > >Hexman wrote: >> Hello All, >> >> How do I limit the number of detail records selected in a Master-Detail set using SQL? >> >> I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've >> been trying with "TOP 3", but can't get anywhere. Using Access 2000. >> >> Something like: >> >> SELECT t1.*, TOP 3 t2.* >> FROM t1, t2 >> WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) >> >> Any help appreciated, >> >> Hexman Hi
I don't think you're going to be able to do this as the "Top x" clause is going to limit your resultset to x number of records, not x number of records for each 'grouping' (i.e. the link between your two tables) so no matter how you try to link the results of this subquery to your master table, you're only ever (at best) going to get x records from the subquery. Cheers Martin Hexman wrote: Show quoteHide quote > Izzy, > > Thanks for the response. I still can't get it to work, either with Access or SS EE. It generates no error during execution, but doesn't return any > rows. If I take out the "(SELECT TOP 3 t2.* FROM t2)" and change all "t3" references to "t2", it retrieves the rows (except too many of them). > > This has me stumped. Any further ideas? > > All I want to do is limit the number of rows returned from t2 to be joined with t1. > > Thanks, > > Hexman > > > On 23 Sep 2006 16:17:22 -0700, "Izzy" <israel.rich***@gmail.com> wrote: > > >Try this: (Or something of the like) > > > >SELECT t1.*, t3.* > >FROM t1 > >INNER JOIN > >(SELECT TOP 3 t2.* > > FROM t2) t3 ON t1.Item = t3.Item > >WHERE (t1.TrnDate = #09/23/06#) > > > >You may even want too use a LEFT OUTER JOIN for this, depends on your > >data. > > > >Izzy > > > >Hexman wrote: > >> Hello All, > >> > >> How do I limit the number of detail records selected in a Master-Detail set using SQL? > >> > >> I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've > >> been trying with "TOP 3", but can't get anywhere. Using Access 2000. > >> > >> Something like: > >> > >> SELECT t1.*, TOP 3 t2.* > >> FROM t1, t2 > >> WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) > >> > >> Any help appreciated, > >> > >> Hexman Martin is right, this cannot be handled in a query.
This will need to be handled in application code. The only way this would work in a query is if the only 1 record was returned by t1. Izzy Pritcham wrote: Show quoteHide quote > Hi > > I don't think you're going to be able to do this as the "Top x" clause > is going to limit your resultset to x number of records, not x number > of records for each 'grouping' (i.e. the link between your two tables) > so no matter how you try to link the results of this subquery to your > master table, you're only ever (at best) going to get x records from > the subquery. > > Cheers > Martin > > Hexman wrote: > > Izzy, > > > > Thanks for the response. I still can't get it to work, either with Access or SS EE. It generates no error during execution, but doesn't return any > > rows. If I take out the "(SELECT TOP 3 t2.* FROM t2)" and change all "t3" references to "t2", it retrieves the rows (except too many of them). > > > > This has me stumped. Any further ideas? > > > > All I want to do is limit the number of rows returned from t2 to be joined with t1. > > > > Thanks, > > > > Hexman > > > > > > On 23 Sep 2006 16:17:22 -0700, "Izzy" <israel.rich***@gmail.com> wrote: > > > > >Try this: (Or something of the like) > > > > > >SELECT t1.*, t3.* > > >FROM t1 > > >INNER JOIN > > >(SELECT TOP 3 t2.* > > > FROM t2) t3 ON t1.Item = t3.Item > > >WHERE (t1.TrnDate = #09/23/06#) > > > > > >You may even want too use a LEFT OUTER JOIN for this, depends on your > > >data. > > > > > >Izzy > > > > > >Hexman wrote: > > >> Hello All, > > >> > > >> How do I limit the number of detail records selected in a Master-Detail set using SQL? > > >> > > >> I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've > > >> been trying with "TOP 3", but can't get anywhere. Using Access 2000. > > >> > > >> Something like: > > >> > > >> SELECT t1.*, TOP 3 t2.* > > >> FROM t1, t2 > > >> WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) > > >> > > >> Any help appreciated, > > >> > > >> Hexman OK, I understand.
Can anyone give an code example of what Izzy suggests?? Thanks, Hexman Show quoteHide quote On 25 Sep 2006 06:03:29 -0700, "Izzy" <israel.rich***@gmail.com> wrote: >Martin is right, this cannot be handled in a query. > >This will need to be handled in application code. > >The only way this would work in a query is if the only 1 record was >returned by t1. > >Izzy > > >Pritcham wrote: >> Hi >> >> I don't think you're going to be able to do this as the "Top x" clause >> is going to limit your resultset to x number of records, not x number >> of records for each 'grouping' (i.e. the link between your two tables) >> so no matter how you try to link the results of this subquery to your >> master table, you're only ever (at best) going to get x records from >> the subquery. >> >> Cheers >> Martin >> >> Hexman wrote: >> > Izzy, >> > >> > Thanks for the response. I still can't get it to work, either with Access or SS EE. It generates no error during execution, but doesn't return any >> > rows. If I take out the "(SELECT TOP 3 t2.* FROM t2)" and change all "t3" references to "t2", it retrieves the rows (except too many of them). >> > >> > This has me stumped. Any further ideas? >> > >> > All I want to do is limit the number of rows returned from t2 to be joined with t1. >> > >> > Thanks, >> > >> > Hexman >> > >> > >> > On 23 Sep 2006 16:17:22 -0700, "Izzy" <israel.rich***@gmail.com> wrote: >> > >> > >Try this: (Or something of the like) >> > > >> > >SELECT t1.*, t3.* >> > >FROM t1 >> > >INNER JOIN >> > >(SELECT TOP 3 t2.* >> > > FROM t2) t3 ON t1.Item = t3.Item >> > >WHERE (t1.TrnDate = #09/23/06#) >> > > >> > >You may even want too use a LEFT OUTER JOIN for this, depends on your >> > >data. >> > > >> > >Izzy >> > > >> > >Hexman wrote: >> > >> Hello All, >> > >> >> > >> How do I limit the number of detail records selected in a Master-Detail set using SQL? >> > >> >> > >> I want to select all master records for a date, but only the first 3 records for the details (based on the primary key of the detail record). I've >> > >> been trying with "TOP 3", but can't get anywhere. Using Access 2000. >> > >> >> > >> Something like: >> > >> >> > >> SELECT t1.*, TOP 3 t2.* >> > >> FROM t1, t2 >> > >> WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) >> > >> >> > >> Any help appreciated, >> > >> >> > >> Hexman Hexman wrote:
> Hello All, Master-Detail set using SQL?> > How do I limit the number of detail records selected in a > records for the details (based on the primary key of the detail record). > I want to select all master records for a date, but only the first 3 I've > been trying with "TOP 3", but can't get anywhere. Using Access 2000. You need to understand what you're doing before you can optimize it :) > > Something like: > > SELECT t1.*, TOP 3 t2.* > FROM t1, t2 > WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) > > Any help appreciated, > > Hexman Now you're creating a dataset that effectively creates a copy of all records in t2 for each entry in t1. If you have alot of records, this will get ouf of hand very quickly (i.e. 2 tables with 1000 records each will cause 10.000 records in memory this way) So using a join like Izzy suggested is usually much better. How about this: Select * from t1 inner join t2 on (t1.item=t2.item) where t1.TrnDate=#09/23/06# and t2.item in (select top 3 item from t2) This should join the 2 tables where the 'item' in the 2 tables match and the date in t1 is the one specified and the items appear in the top 3 of t2. There is no sort order given to t2, so results may be unpredictable. -- Rinze van Huizen C-Services Holland b.v Hi Rinze
You're absolutely right - I was trying to think of how to limit the result set in the detail selection before the join happened and completely missed the use of IN() along with a subquery. I knew I should have waiting longer before posting! As for performance on this - as you say, it sucks! Mainly because, as far as I understand, it's running the subquery for each and every row in the resultset. Having just ran a quick test on a couple of handy tables I have here (only returning 1500 rows in the end results) and the performance was way too slow to be acceptable for me so depending on the need I think I'd probably just do a straight join and then limit the number that I display client-side (again, depending on the volume of data that's got to travel the wire and how frequently etc). Still - at least I can cross "learn something new today" off my TODO list! Martin C-Services Holland b.v. wrote: Show quoteHide quote > Hexman wrote: > > Hello All, > > > > How do I limit the number of detail records selected in a > Master-Detail set using SQL? > > > > I want to select all master records for a date, but only the first 3 > records for the details (based on the primary key of the detail record). > I've > > been trying with "TOP 3", but can't get anywhere. Using Access 2000. > > > > Something like: > > > > SELECT t1.*, TOP 3 t2.* > > FROM t1, t2 > > WHERE (t1.item = t2.item) AND (t1.TrnDate = #09/23/06#) > > > > Any help appreciated, > > > > Hexman > > You need to understand what you're doing before you can optimize it :) > Now you're creating a dataset that effectively creates a copy of all > records in t2 for each entry in t1. If you have alot of records, this > will get ouf of hand very quickly (i.e. 2 tables with 1000 records each > will cause 10.000 records in memory this way) So using a join like Izzy > suggested is usually much better. > > How about this: > > Select * > from t1 inner join t2 on (t1.item=t2.item) > where t1.TrnDate=#09/23/06# > and t2.item in > (select top 3 item from t2) > > This should join the 2 tables where the 'item' in the 2 tables match and > the date in t1 is the one specified and the items appear in the top 3 of > t2. There is no sort order given to t2, so results may be unpredictable. > > > -- > Rinze van Huizen > C-Services Holland b.v 
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