Thread: PL/PGSQL help for getting number of rows matched.
Hi,
We need to implement following logic efficiently.
SELECT * from some_table where .... [ Query 1 ]
IF rows_matched = 1 THEN
use the single row that matched.
ELSIF
loop thru the results of [Query 1]
END IF;
Currently i am doing select count(*) for getting rows_matched
in the top and repeating the same query in both branches of IF
to get the data of matching rows.
I have tried GET DIAGNOSTICS ROW_COUNT but for
"SELECTS" if returns 0 or 1 based on matching
I am sure there exists better methods. Kindly post a link
to better documentation of pl/pgsql or point out section in
the standard docs that discuss this issue.
Regds
Mallah.
Hello, it isn't problem. You can write SELECT INTO .... IF FOUND THEN ... END IF or SELECT INTO .. GET DIAGNOSTICS variable = ROW_COUNT; IF variable > 0 THEN ... END IF You can see on http://developer.postgresql.org/docs/postgres/plpgsql-statements.html#PLPGSQL-SELECT-INTO Regards Pavel On Mon, 10 Nov 2003, Rajesh Kumar Mallah wrote: > > Hi, > > We need to implement following logic efficiently. > > SELECT * from some_table where .... [ Query 1 ] > > IF rows_matched = 1 THEN > > use the single row that matched. > > ELSIF > > loop thru the results of [Query 1] > > END IF; > > > Currently i am doing select count(*) for getting rows_matched > in the top and repeating the same query in both branches of IF > to get the data of matching rows. > > I have tried GET DIAGNOSTICS ROW_COUNT but for > "SELECTS" if returns 0 or 1 based on matching > > I am sure there exists better methods. Kindly post a link > to better documentation of pl/pgsql or point out section in > the standard docs that discuss this issue. > > Regds > Mallah. > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 7: don't forget to increase your free space map settings >
On Mon, 10 Nov 2003, Pavel Stehule wrote: > Hello, > > it isn't problem. You can write > > SELECT INTO .... > IF FOUND THEN > ... > END IF > > or > > SELECT INTO .. > GET DIAGNOSTICS variable = ROW_COUNT; > IF variable > 0 THEN > ... > END IF > > You can see on > http://developer.postgresql.org/docs/postgres/plpgsql-statements.html#PLPGSQL-SELECT-INTO Probably sectino 37.7.4 of the docs ( in http://developer.postgresql.org/docs/postgres/plpgsql-control-structures.html ) is a better source as shown lower. > > On Mon, 10 Nov 2003, Rajesh Kumar Mallah wrote: > > > > > Hi, > > > > We need to implement following logic efficiently. > > > > SELECT * from some_table where .... [ Query 1 ] > > > > IF rows_matched = 1 THEN > > > > use the single row that matched. > > > > ELSIF > > > > loop thru the results of [Query 1] > > > > END IF; > > > > > > Currently i am doing select count(*) for getting rows_matched > > in the top and repeating the same query in both branches of IF > > to get the data of matching rows. > > > > I have tried GET DIAGNOSTICS ROW_COUNT but for > > "SELECTS" if returns 0 or 1 based on matching > > > > I am sure there exists better methods. Kindly post a link > > to better documentation of pl/pgsql or point out section in > > the standard docs that discuss this issue. DECLARE tup RECORD; BEGIN FOR tup IN select * from mytable LOOP Do the required action END LOOP; END Indeed, I'm not even sure how to loop through the results of the query using the scheme you show above. What do you assign the results of the select to? -- Nigel Andrews
Maybe you can use a for if there is only one row it will do the job just
like if there were many rows:
FOR referrer_keys IN SELECT * FROM cs_referrer_keys ORDER BY try_order
LOOP
a_output := a_output || '' IF v_'' || referrer_keys.kind || '' LIKE
''''''''''
|| referrer_keys.key_string || '''''''''' THEN RETURN
''''''
|| referrer_keys.referrer_type || ''''''; END IF;'';
END LOOP;
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On Monday 10 Nov 2003 5:38 pm, Pavel Stehule wrote: > Hello, > > it isn't problem. You can write > > SELECT INTO .... > IF FOUND THEN > ... > END IF I have *different* logic for match=1 and for match > 1 , so FOUND is not a solution as manual says. There is a special variable named FOUND of type boolean. FOUND starts out false within each PL/pgSQL function. It is set by each of the following types of statements: Section 19.5.5 http://www.postgresql.org/docs/7.3/static/plpgsql-statements.html > > or > > SELECT INTO .. > GET DIAGNOSTICS variable = ROW_COUNT; > IF variable > 0 THEN > ... > END IF Even this does not solve my problem. See my actual code and the output. -- ***************** CODE ******************* CREATE OR REPLACE FUNCTION general.copy_accounts() returns integer AS ' DECLARE users_c CURSOR FOR SELECT userid FROM general.user_accounts where userid=46 ; userid_v int; i int; matched int; rec RECORD; BEGIN OPEN users_c; i := 1; LOOP FETCH users_c INTO userid_v; EXIT WHEN NOT FOUND ; SELECT INTO rec profile_id from general.profile_master where userid=userid_v; GET DIAGNOSTICS matched = ROW_COUNT; RAISE INFO ''matched = % '' , matched; SELECT INTO matched count(*) from general.profile_master where userid=userid_v; RAISE INFO ''matched = % '' , matched; EXIT; END LOOP; CLOSE users_c; RETURN 1; END ' LANGUAGE 'plpgsql'; -- ------ CODE ENDS RESULTS BELOW: tradein_clients=# SELECT copy_accounts(); INFO: matched = 1 INFO: matched = 3 Note that matched was 3 but in first place it did not come. +---------------+ | copy_accounts | +---------------+ | 1 | +---------------+ (1 row) Time: 386.76 ms tradein_clients=# Regds Mallah. > > You can see on > http://developer.postgresql.org/docs/postgres/plpgsql-statements.html#PLPGS >QL-SELECT-INTO > > Regards > Pavel > > On Mon, 10 Nov 2003, Rajesh Kumar Mallah wrote: > > Hi, > > > > We need to implement following logic efficiently. > > > > SELECT * from some_table where .... [ Query 1 ] > > > > IF rows_matched = 1 THEN > > > > use the single row that matched. > > > > ELSIF > > > > loop thru the results of [Query 1] > > > > END IF; > > > > > > Currently i am doing select count(*) for getting rows_matched > > in the top and repeating the same query in both branches of IF > > to get the data of matching rows. > > > > I have tried GET DIAGNOSTICS ROW_COUNT but for > > "SELECTS" if returns 0 or 1 based on matching > > > > I am sure there exists better methods. Kindly post a link > > to better documentation of pl/pgsql or point out section in > > the standard docs that discuss this issue. > > > > Regds > > Mallah. > > > > > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 7: don't forget to increase your free space map settings
On Monday 10 Nov 2003 6:05 pm, Nigel J. Andrews wrote:
> DECLARE
> tup RECORD;
> BEGIN
> FOR tup IN select * from mytable
> LOOP
> Do the required action
> END LOOP;
> END
>
> Indeed, I'm not even sure how to loop through the results of the query
> using the scheme you show above. What do you assign the results of the
> select to?
My working code which i think can be improved is below
note that i treat match=1 and match>1 differently.
I hope it will answer both of your question.
Thanks everyone for the responses though :)
Pl/Pgsql itself seems to be the most mature of all PL
hence we have decided to shift our business logic from
perl layer to DataBase for obvious gains.
-- Actual Code-------
CREATE OR REPLACE FUNCTION general.copy_accounts() returns integer AS
'
DECLARE
users_c CURSOR FOR SELECT userid FROM general.user_accounts ;
userid_v int;
i int;
matched int;
rec RECORD;
BEGIN
OPEN users_c;
i := 1;
LOOP
FETCH users_c INTO userid_v;
EXIT WHEN NOT FOUND ;
SELECT INTO matched count(*) from general.profile_master where userid=userid_v;
IF matched = 1 THEN
SELECT INTO rec email,title1 , fname1 , mname1 , lname1 , desg1 , mobile from
general.profile_masterwhere userid=userid_v;
ELSIF matched > 1 THEN
-- multiple profiles then get the profile that
-- has highest score.
SELECT INTO rec email,title1 , fname1 , mname1 , lname1 , desg1 , mobile,source
from general.profile_master join
general.temp_source_priority using(source) where userid=userid_v
order by profile_score(email,title1 , fname1 , mname1 , lname1 , desg1 , mobile) desc limit 1;
END IF;
IF matched >= 1 THEN
i := i + 1;
UPDATE general.user_accounts set
email= rec.email,
title= rec.title1 ,
fname= rec.fname1 ,
mname= rec.mname1 ,
lname= rec.lname1 ,
desg = rec.desg1 ,
mobile= rec.mobile where userid = userid_v;
END IF;
IF i % 100 = 0 THEN
RAISE INFO '' copied % accounts '' , i;
END IF;
END LOOP;
CLOSE users_c;
RAISE INFO '' Successfully finished with % accounts '' , i;
RETURN 1;
END
' LANGUAGE 'plpgsql';
Once again , I have different logic based on match, i need to know a prioi the number of matches. See the actual code in response to Nigel . Thanks for your response. regds mallah. On Monday 10 Nov 2003 6:57 pm, Jaime Casanova wrote: > Maybe you can use a for if there is only one row it will do the job just > like if there were many rows: > > FOR referrer_keys IN SELECT * FROM cs_referrer_keys ORDER BY try_order > LOOP > a_output := a_output || '' IF v_'' || referrer_keys.kind || '' LIKE > '''''''''' > > || referrer_keys.key_string || '''''''''' THEN RETURN > > '''''' > > || referrer_keys.referrer_type || ''''''; END IF;''; > > END LOOP; > > _________________________________________________________________ > Add photos to your e-mail with MSN 8. Get 2 months FREE*. > http://join.msn.com/?page=features/featuredemail > > > ---------------------------(end of broadcast)--------------------------- > TIP 6: Have you searched our list archives? > > http://archives.postgresql.org