Обсуждение: using Avg()

I have a table with a column named SwErr   (Switch Error) with int values
date with datetime values and SwID with char(3)
I am trying to get a subset back where the folowing is true
select the avg(SwErr) for the last 30 days where SwId = 'XX1'
Select the value of todays value of SwErr where SwId = 'XX1'
if todays value of SwErr is greater than 4 times the SwErr Average return in
the value
TIA
Mark Connelly


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>
> I have a table with a column named SwErr   (Switch Error) with int
values
> date with datetime values and SwID with char(3)
> I am trying to get a subset back where the folowing is true
>
> select the avg(SwErr) for the last 30 days where SwId = 'XX1'
> Select the value of todays value of SwErr where SwId = 'XX1'
> if todays value of SwErr is greater than 4 times the SwErr Average
return in
> the value
>
Looks like you could use a plpgsql function, something like (untested)

CREATE OR REPLACE FUNCTION
get_dated_SwErr(CHAR) RETURNS INTEGER AS '
DECLAREthisSwID       ALIAS FOR $1;todaysSwErr    INT;avgSwErr       INT;avg4SwErr      INT;dateLimit      TIMESTAMP;
BEGIN

SELECT INTO dateLimit current_date - ''30 days''::interval ;

SELECT INTO todaysSwErr SwErr FROM <SwTable>WHERE SwID = thisSwID AND SwDate = current_date ;

SELECT INTO avgSwErr AVG(SwErr)::int FROM <SwTable>WHERE SwID = thisSwID AND SwDate BETWEEN current_date AND dateLimit
;

avg4SwErr := avgSwErr * 4 ;

IF todaysSwErr > avg4SwErr THENRETURN todaysSwErr;
ELSERETURN avgSwErr;
END IF;

END;
' LANGUAGE 'plpgsql' ;

then
SELECT SwID, get_dated_SwErr(SwID) FROM <SwTable>WHERE SwID = 'XX1' AND SwDate = current_date ;
should bring up the result.

Regards, Christoph