带IF语句的MySQL存储过程

Question

I need to define a mysql stored procedure that if you pass it a parameter, uses it in a select query and if you don't then it doesn't.

Here's what i have, and it's not working :

IF (selected_category IS NULL) then

SELECT i.id, i.name, i.summary, i.description, i.location, c.name AS 'category_name' 
FROM items i, categories c WHERE i.category_id = c.id;

ELSE IF (selected_category IS NOT NULL) then

SELECT i.id, i.name, i.summary, i.description, i.location, c.name AS 'category_name'
FROM items i, categories c WHERE i.category_id = c.id AND c.name LIKE selected_category;

END IF

I've also tried, instead of ELSE IF , to write ELIF , END IF; and then a new IF but nothing wants to work.

When I click the Create Procedure it always displays an error unless I comment out everything below the first SELECT .

Help would be much appreciated. Thank you.

Answer 1

You can use only one query:

SELECT i.id, i.name, i.summary, i.description, i.location, c.name AS 'category_name'
FROM items i, categories c 
WHERE i.category_id = c.id 
AND IF(selected_category IS NOT NULL, c.name LIKE CONCAT('%', selected_category,'%'), TRUE);

On a side note, please use explicit joins instead of implicit.

ps: I realize I didn't really answer your question, I just provided an alternative. I think you just missed the ELSEIF statement. You are using ELSE IF and you tried ELIF , but it's apparently not the correct syntax .