SQL query …multiple max value selection. Help need

问题:

Business World 1256987 monthly 10 2009-10-28

Business World 1256987 monthly 10 2009-09-23

Business World 1256987 monthly 10 2009-08-18

Linux 4 U 456734 monthly 25 2009-12-24

Linux 4 U 456734 monthly 25 2009-11-11

Linux 4 U 456734 monthly 25 2009-10-28

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I get this result with the query:

SELECT DISTINCT ljm.journelname,ljm. subscription_id,
    ljm.frequency,ljm.publisher, ljm.price, ljd.receipt_date 
FROM lib_journals_master ljm,
    lib_subscriptionhistory 
    lsh,lib_journal_details ljd 
WHERE ljd.journal_id=ljm.id 
ORDER BY ljm.publisher

---

What I need is the latest date in each journal?

I tried this query:

SELECT DISTINCT ljm.journelname, ljm.subscription_id,
    ljm.frequency, ljm.publisher, ljm.price,ljd.receipt_date
FROM lib_journals_master ljm,
    lib_subscriptionhistory lsh,
    lib_journal_details ljd
WHERE ljd.journal_id=ljm.id 
AND ljd.receipt_date = (
    SELECT max(ljd.receipt_date) 
    from lib_journal_details ljd)

---

But it gives me the maximum from the entire column. My needed result will have two dates (maximum of each magazine), but this query gives me only one?

回答1:

You should use Group By if you need the Max from date. Should look something like this:

SELECT 
   ljm.journelname
   , ljm.subscription_id
   , ljm.frequency
   , ljm.publisher
   , ljm.price
   , **MAX(ljd.receipt_date)**
FROM 
   lib_journals_master ljm
   , lib_subscriptionhistory lsh
   , lib_journal_details ljd
WHERE 
   ljd.journal_id=ljm.id 
GROUP BY 
   ljm.journelname
   , ljm.subscription_id
   , ljm.frequency
   , ljm.publisher
   , ljm.price

回答2:

You could change the WHERE statement to look up the last date for each journal:

AND ljd.receipt_date = (
    SELECT max(subljd.receipt_date) 
    from lib_journal_details subljd
    where subljd.journelname = ljd.journelname)

Make sure to give the table in the subquery a different alias from the table in the main query.

回答3:

Something like this should work for you.

SELECT ljm.journelname
       , ljm.subscription_id
       , ljm.frequency
       , ljm.publisher
       , ljm.price
       ,md.max_receipt_date
FROM lib_journals_master ljm
    , (    SELECT journal_id
            , max(receipt_date) as max_receipt_date
           FROM lib_journal_details 
           GROUP BY journal_id) md
WHERE ljm.id = md.journal_id
/

Note that I have removed the tables from the FROM clause which don't contribute anything to the query. You may need to replace them if yopu simplified your scenario for our benefit.

回答4:

Separate this into two queries one will get journal name and latest date

declare table @table (journalName as varchar,saleDate as datetime)

insert into @table
select journalName,max(saleDate) from JournalTable group by journalName

select all fields you need from your table and join @table with them. join on journalName.

回答5:

Sounds like top of group. You can use a CTE in SQL Server:

;WITH journeldata AS
(
SELECT 
     ljm.journelname
    ,ljm.subscription_id
    ,ljm.frequency
    ,ljm.publisher
    ,ljm.price
    ,ljd.receipt_date
    ,ROW_NUMBER() OVER (PARTITION BY ljm.journelname ORDER BY ljd.receipt_date DESC) AS RowNumber
FROM 
     lib_journals_master ljm
    ,lib_subscriptionhistory lsh
    ,lib_journal_details ljd 
WHERE 
    ljd.journal_id=ljm.id
    AND ljm.subscription_id = ljm.subscription_id
)
SELECT
     journelname
    ,subscription_id
    ,frequency
    ,publisher
    ,price
    ,receipt_date
FROM journeldata
WHERE RowNumber = 1