Logic condition to avoid duplicate entries in stored procedure - mysql

Question

I have the following stored procedure . I'm trying to insert the users from the table usuaris, whose admin variable is equal to 1, into the table that the stored procedure creates with the name( nombre varchar(50)) that is passed as a parameter.
When the procedure is called, it duplicates the user 'mary' with id 4. I've tried a couple of ways to implement the logic condition in order to avoid the duplication, but still, I'm missing something and I can't get the desired result. In the code below, the logic condition before the insertion is the last thing I've tried. Any ideas?
Thanks.
CREATE DEFINER=`root`#`localhost` PROCEDURE `createNewtable`(nombre varchar(50))
BEGIN
/*variable declaration*/
declare centinela int ;
declare id1 int ;
declare nom1 varchar(50);
declare admin1 enum('0','1') ;
declare cadena varchar(100); /*string to concatenate table creation and insertion*/
/*cursor declaration*/
declare cursor1 cursor for select * from users.usuaris where admin = '1' ;
declare continue handler for not found set #centinela = 1 ;
/*create the table with the name that's passed as parameter*/
set #cadena=concat("create table ",nombre,
"(
id2 int not null primary key,
nom2 varchar(50),
admin2 enum ('0','1')
)" );
prepare stmt from #cadena ;
execute stmt ;
deallocate prepare stmt;
/* loop that fetches the data from the table usuaris and
inserts them into the newly created table. */
set #centinela = 0 ;
open cursor1 ;
bucle: loop
fetch cursor1 into id1,nom1,admin1 ;
if ( centinela = 1 ) then
leave bucle ;
end if ;
/*logic condition to avoid entry duplication */
if not exists (select * from users.usuaris where admin='1' and id=#id1) then
set #cadena=concat("insert into ",nombre," values( ",id1,",'",nom1,"','",admin1,"')");
end if;
select #cadena;
prepare stmt from #cadena;
execute stmt ;
deallocate prepare stmt;
end loop bucle;
close cursor1;
END
Here is the single-table database of users :
create database if not exists `users` ;
use `users` ;
create table usuaris(
id int not null auto_increment primary key ,
nom varchar(50),
admin enum ('0','1')
);
insert into usuaris(id,nom,admin)
values
(1,'jose','1'),
(2,'maria','0'),
(3,'frank','1'),
(4,'mary','1'),
(5,'godfrey','0') ;

Answer 1

Also it has to duplicate jose. The reason of duplication - if the IF statement isn't TRUE then you don't set the new #cadena variable BUT anyway execute PREVIOUS #cadena statement. You should move execution into the IF statement also:
if not exists (select * from users.usuaris where admin='1' and id=#id1) then
set #cadena=concat("insert into ",nombre," values( ",id1,",'",nom1,"','",admin1,"')");
select #cadena;
prepare stmt from #cadena;
execute stmt ;
deallocate prepare stmt;
end if;
Also in SQL you should always try to avoid loops if it possible and use SQL statements instead.
You can replace your loop with one SQL statement:
INSERET INTO NEW_TABLE_NAME_HERE
SELECT id1,nom1,admin1
FROM users.usuaris where admin<>'1'
Further more you can use SELECT INTO statement syntax to automatically create new table without CREATE TABLE statement:
SELECT id1 as id2,
nom1 as nom2,
admin1 as admin2
INTO NEW_TABLE_NAME_HERE
FROM users.usuaris where admin<>'1'

Answer 2

Change ur below code to my new code and try-
Existing Code
if not exists (select * from users.usuaris where admin='1' and id=#id1) then
set #cadena=concat("insert into ",nombre," values( ",id1,",'",nom1,"','",admin1,"')");
end if;
select #cadena;
prepare stmt from #cadena;
execute stmt ;
deallocate prepare stmt;
New Code-
SET #cnt=SELECT count(*) FROM users.usuaris WHERE admin='1' AND id=#id1
IF #cnt>0 THEN
SET #cadena=CONCAT("insert into ",nombre," values( ",id1,",'",nom1,"','",admin1,"')");
prepare stmt from #cadena;
execute stmt ;
deallocate prepare stmt;
end if;