gestion des paramètres null dans la procédure mysql - ne fonctionne pas

Question

Je passe la procédure null à below car elle ne renvoie aucune valeur même si les données sont présentes dans la table?

appelez view_ads (NULL, 'vehicles', 9);

appelez view_ads ('placename', null, 9);

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ci-dessous est le code

delimiter $$ 
drop procedure view_ads$$ 
create procedure view_ads (place_name varchar(200),category_name varchar(200),pagecount int(8)) 
begin 
declare lowerval int(8); 
declare higherval int(8); 
set lowerval= pagecount-9; 
set higherval=pagecount; 
if isnull(place_name) then 

SET @sql = CONCAT("select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='N' and (category ='",category_name,"' or subcategory='",category_name,"') 
union all 
select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='Y' and (category ='",category_name,"' or subcategory='",category_name,"') 
order by automated asc,posteddate desc 
limit ",lowerval,",",higherval) 
; 
elseif ISNULL(category_name) then 
SET @sql = CONCAT("select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='N' and (state ='",place_name,"' or city='",place_name,"') 
union all 
select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='Y' and (state ='",place_name,"' or city='",place_name,"') 
order by automated asc,posteddate desc 
limit ",lowerval,",",higherval) 
; 
else 
SET @sql = CONCAT("select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='N' and (state ='",place_name,"' or city='",place_name,"') and (category ='",category_name,"' or subcategory='",category_name,"') 
union all 
select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='Y' and (state ='",place_name,"' or city='",place_name,"') and (category ='",category_name,"' or subcategory='",category_name,"') 
order by automated asc,posteddate desc 
limit ",lowerval,",",higherval) 
; 
PREPARE stmt FROM @sql; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 
end if; 
end$$ 

Answer 1

Essayez de comparer avec une chaîne vide, quelque chose comme ceci:

delimiter $$ 
drop procedure view_ads$$ 
create procedure view_ads (place_name varchar(200),category_name varchar(200),pagecount int(8)) 
begin 
declare lowerval int(8); 
declare higherval int(8); 
set lowerval= pagecount-9; 
set higherval=pagecount; 

if place_name = '' then 
SET @condition = CONCAT("and (category ='",category_name,"' or subcategory='",category_name,"')"); 
else if category_name = '' then 
SET @condition = CONCAT("(state ='",place_name,"' or city='",place_name,"')"); 
else 
SET @condition = CONCAT("(state ='",place_name,"' or city='",place_name,"') and (category ='",category_name,"' or subcategory='",category_name,"')"); 

SET @SQL = CONCAT("select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='N' ",condition," 
union all 
select idads_list,category,subcategory,state,city,title, 
     title_decode,phonenumber,userid,description,DATE_FORMAT(ad_date,'%d-%M-%Y %H:%i:%s') posteddate,automated 
     from ads_list 
where automated='Y' ",condition," 
order by automated asc,posteddate desc 
limit ",lowerval,",",higherval) 
; 
PREPARE stmt FROM @sql; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 
end if; 
end$$ 

aussi j'ai modifié un peu votre procédure pour être plus courte.