SQL variable in IF exists - mysql

Question

I can't figure out the correct way to assign query output into a variable that i could later use in an INSERT clause.
The error I get is
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SET #lennuid = (select lend_id from lend where sihtpunkt=in_kuhu AND kuupaev=in_' at line 8
I've tried looking at every guide on variables in SQL but none of them could help me solve this.
Iam using the below code:
CREATE PROCEDURE proov(
in_kuhu varchar(50), in_nimi1 varchar(50), in_nimi2 varchar(50), in_adre varchar(50), in_telo varchar(20), in_email varchar(100), in_date date)
BEGIN
DECLARE viga INTEGER DEFAULT 0 ;
DECLARE lennuid INT;
START TRANSACTION;
IF exists (
SET #lennuid = (select lend_id from lend where sihtpunkt=in_kuhu AND kuupaev=in_date)) THEN
INSERT INTO broneering
(lend_id, bron_aeg, eesnim, perenimi, aadress, telefon, email)
VALUES
(lennuid, NOW(), in_nimi1, in_nimi2, in_adre, in_telo, in_email);
ELSE
set viga=1;
SELECT 'Muudatus ebaonnestus ',viga;
END IF;
IF viga=0 then
COMMIT;
select 'korras';
ELSE
select 'tagasi';
ROLLBACK;
END IF;

Answer 1

THEN causing the issue.
IF exists (
SET #lennuid = (select lend_id from lend where sihtpunkt=in_kuhu AND kuupaev=in_date))
BEGIN -- Instead of THEN use BEGIN , END
INSERT INTO broneering
(lend_id, bron_aeg, eesnim, perenimi, aadress, telefon, email)
VALUES
(lennuid, NOW(), in_nimi1, in_nimi2, in_adre, in_telo, in_email);
END
ELSE
BEGIN
set viga=1;
SELECT 'Muudatus ebaonnestus ',viga;
END
END IF;

Answer 2

You might want to use SELECT INTO:
select lend_id into #lennuid
from lend
where sihtpunkt=in_kuhu AND kuupaev=in_date;
Alternatively:
select #lennuid := lend_id
from lend
where sihtpunkt=in_kuhu AND kuupaev=in_date;
Either way works the same, then you can use that variable however you like...
In your particular example, though, the problem is actually how your exists is being used along with the set. To fix this, use the following:
IF exists (select lend_id from lend where sihtpunkt=in_kuhu AND kuupaev=in_date) THEN ...
What the problem here is, is you were setting a variable with SET inside of the EXISTS check.
Or you could do your select first as a COUNT into a numeric variable:
DECLARE cnt INTEGER;
select Count(lend_id) into #cnt
from lend
where sihtpunkt=in_kuhu
and kuupaev=in_date;
IF #cnt > 0 THEN
END IF;