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POMinimum and maximum values from different mysql tables
 

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  1. POMinimum and maximum values from different mysql tables
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    <p>I have two tables: TableA and TableB. Both have "dates" and "rates" fields. I want to have minimum rates of TableA and their dates; and maximum rates of TableB and their dates. Also, I like to list them for each month and year. </p> <p>I use the query below to get minimum and maximum rates from <strong>one table</strong>. But I could not figure out how to get minimum rates from TableA maximum rates from TableB.</p> <pre><code>SELECT MIN(rate) AS minRate, (SELECT date FROM TableA WHERE rate = min(t2.rate) and month(date) = month(t2.date) and year(date) = year(t2.date) limit 1 ) as minDate, MONTHNAME(date) as MN, YEAR(date) as YN, MAX(rate) AS maxRate, (SELECT date FROM TableAs WHERE rate = max(t2.rate) and month(date) = month(t2.date) and year(date) = year(t2.date) limit 1) as maxDate FROM TableA t2 GROUP BY YEAR(date) , MONTH(date)"; </code></pre> <p><strong>EDIT 1:</strong> I ended up with this.</p> <pre><code>SELECT a.MinYear AS Year, a.MinMonth AS Month, a.MinRate, b.MaxRate, a.MinDate, b.MaxDate FROM (SELECT YEAR(date) AS MinYear, MONTH(date) AS MinMonth, MIN(rate) AS MinRate, (SELECT date FROM $TableA WHERE rate = MIN(t2.rate) AND YEAR(date) = YEAR(t2.date) AND MONTH(date) = MONTH(t2.date) limit 1) AS MinDate FROM $TableA t2 GROUP BY MinYear, MinMonth ) AS a JOIN (SELECT YEAR(date) AS MaxYear, MONTH(date) AS MaxMonth, MAX(rate) AS MaxRate, (SELECT date FROM $TableB WHERE rate = MAX(t3.rate) AND YEAR(date) = YEAR(t3.date) AND MONTH(date) = MONTH(t3.date) limit 1) AS MaxDate FROM $TableB t3 GROUP BY MaxYear, MaxMonth ) AS b ON a.MinYear = b.MaxYear AND a.MinMonth = b.MaxMonth ORDER BY Year, Month </code></pre> <p><strong>EDIT 2</strong> Jonathan Leffler's query (with minor changes after testing) performs better:</p> <pre><code>SELECT a.MinYear AS Year, a.MinMonth AS Month, a.MinDate, a.MinRate, b.MaxDate, b.MaxRate FROM (SELECT n.MinYear, n.MinMonth, a.Date AS MinDate, n.MinRate FROM $TableA AS a JOIN (SELECT YEAR(date) AS MinYear, MONTH(date) AS MinMonth, MIN(rate) AS MinRate FROM $TableA GROUP BY MinYear, MinMonth ) AS n ON a.Rate = n.MinRate AND YEAR(a.Date) = n.MinYear AND MONTH(a.Date) = n.MinMonth ) AS a JOIN (SELECT x.MaxYear, x.MaxMonth, b.Date AS MaxDate, x.MaxRate FROM $TableB AS b JOIN (SELECT YEAR(date) AS MaxYear, MONTH(date) AS MaxMonth, MAX(rate) AS MaxRate FROM $TableB GROUP BY MaxYear, MaxMonth ) AS x ON b.Rate = x.MaxRate AND YEAR(b.Date) = x.MaxYear AND MONTH(b.Date) = x.MaxMonth ) AS b ON a.MinYear = b.MaxYear AND a.MinMonth = b.MaxMonth ORDER BY Year, Month"; </code></pre>
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    1. COwhat columns should be used to connect rows from the two tables? do you literally want just one row?
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    2. CO@Bohemian: I want to have minimum value of each month from TableA and maximum value of each month from TableB
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    3. COIf you can get the query above to work for one table, couldn't you just create 2 queries that pull the information you want and then do an inner join on the month and year? E.g., Select * from (select * from tablea) as t1 inner join (select * from tableb) as t2 on t1.year(date) = t2.year(date) AND t1.month(date) = t2.month(date)
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