Delete from a SQL Table using a couple JOINs - sql

Question

There are 4 Tables:
Users: id,name
Albums: id,user_id
Pictures: id,picture_name,album_id
Tags: picture_id , user_id
I need to write 2 commands:
- a command which deletes a picture by its name -
which means, removing it from the "Tags" table and from the "Pictures" table.
- a command which adds a tag to a picture of a User.
I have tried so far those two commands (which don't seem to work):
Deleting from the tags table:
DELETE FROM Tags
JOIN Albums
ON Users.id=Albums.user_id
JOIN PICTURES
ON Pictures.album_id = Albums.id
WHERE Pictures.name LIKE "pic_name.png" ;
Deleting from the pictures table:
DELETE FROM Pictures
WHERE Pictures.name LIKE "pic_name.png" ;
Adding a tag of " user1 " on picture "pic_name2.png" to the Tags table:
INSERT INTO Tags (user_id,picture_id) SELECT Users.id, Pictures.id FROM Albums JOIN Users ON Users.id=Albums.user_id JOIN PICTURES ON Pictures.album_id = Albums.id WHERE Users.name LIKE "user1" and Pictures.name= "pic_name2.png";
please help me write those queries correctly ...

Answer 1

try like below
delete from Tags
where user_id in
( select user_id from Albums
JOIN PICTURES
ON PICTURES.album_id = Albums.id
WHERE Pictures.name LIKE '%pic_name.png%'
)
2nd query
DELETE FROM Pictures
WHERE Pictures.name LIKE '%pic_name.png%'
and 3rd query only need change where
WHERE Users.name ='user1' and Pictures.name= 'pic_name2.png'

Answer 2

You don't need to join any tables to delete the rows:
delete from tags
where picture_id = (
select id from pictures
where picture_name = 'pic_name.png'
);
delete from pictures
where picture_name = 'pic_name.png';
The tables users and pictures cannot and do not need to be joined.
You can insert a new row like this:
insert into tags (user_id, picture_id) values
(
(select id from users where name = 'user1'),
(select id from pictures where picture_name = 'pic_name2.png')
);
As you can see I changed all like to = because this is what you need in this case.
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