Mysql Loop through selected column and execute Insert query in the loop - mysql

Question

I'm trying to loop over selected slugs and execute little complicated INSERT INTO SELECT query.
slugs[iteration] usage is not a correct mysql syntax. But I have to access fetched slugs one by one inside the query. How Could I achieve that ?
DELIMITER $$
CREATE PROCEDURE create_sitemap_from_slugs()
BEGIN
SELECT `slug` INTO slugs FROM slug_table;
SELECT COUNT(*) INTO count FROM slug_table;
SET iteration = 0;
START TRANSACTION;
WHILE iteration < count DO
INSERT INTO line_combinations
SELECT REPLACE(`line`, '{a}', slugs[iteration]) AS `line`
FROM line_combinations
WHERE `line` LIKE CONCAT('%/', '{a}', '%');
SET iteration = iteration + 1;
END WHILE;
COMMIT;
END
$$
DELIMITER ;
Btw, I don't want to use any external programming language to make this, this procedure will be working for billions of rows. I read Loops in SQL is not a good way due to performance concerns.
If you suggest another way I would accept this also.
I asked another detailed question but couldn't get an answer. if you would like to check that also : https://stackoverflow.com/questions/35320494/fetch-placeholders-from-table-and-place-into-generated-line-combination-pattern

Answer 1

So for each line with {a} you need to insert COUNT(*) from slug_table times values filled with slug value.
It seems you can do that just in one INSERT from SELECT
INSERT INTO line_combinations
(SELECT REPLACE(lc.line, '{a}', st.slug) AS `line`
FROM line_combinations lc, slug_table st
WHERE lc.line LIKE CONCAT('%/', '{a}', '%');
UPDATE:
You can create a temp table line_combinations2 and insert all the records
FROM line_combinations
WHERE line LIKE CONCAT('%/', '{a}', '%')
into the temp table. Then just use the temp table in the INSERT instead of original one