Andreas Andreas - 1 month ago 7
SQL Question

Insert data from another table with a loop in mysql

I could solve it with

php
or some other language but I am keen to learn more SQL.

Is there a way to solve this:

I have two tables (and I can't change the structure), one
content
with some data and the other
content_info
with some additional information. They are related that way:
content.id = content_info.content_id
.

What I would like to do: If there is no dataset in
content_info
but in
content
, I would like to copy it over, that at the end there are the same number of datasets in both tables. I tried it that way, but unfortunately it doesn't work:

...
BEGIN
(SELECT id, ordering FROM content;)
cont:LOOP
@cid = SELECT content_id FROM content_info WHERE content_id = (id)
IF @cid != (id) THEN
INSERT INTO content_info SET content_id = (id), ordering = (ordering)
ITERATE cont;
END IF;
END LOOP cont;
END
..


Has someone an idea, or isn't it possible at the end? Thanks in advance!

Answer

You can use INSERT IGNORE to insert new rows but do nothing if there's already a row in the table that would cause a duplicate entry error.

INSERT IGNORE INTO jos_content_frontpage (content_id, ordering)
SELECT id, ordering FROM jos_content
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