mysql error 1175 while using inner query - mysql

Question

Let's say I have 2 tables - item_images and images.
When I run query
SELECT image_id FROM item_images WHERE item_id=1
I get image_id values 5, 6
When I run
DELETE FROM images WHERE id in (5, 6);
It also works and deletes these 2 rows.
But when I try to chain these 2 queries together, it fails with error 1175.
DELETE FROM images WHERE id in (SELECT image_id FROM item_images WHERE item_id=1);
Error Code:
1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Editor and reconnect. 0.000 sec
id field is set as private key, not null.
Why does this happen if if id in WHERE is clearly private key?
Is the only way to go around this is to disable safe mode, or is there another way?
Thanks!

Answer 1

Assuming id column (images table) is always greater than zero (0):
mysql> SET SESSION SQL_SAFE_UPDATES := 1;
Query OK, 0 rows affected (0.00 sec)
mysql> DROP TABLE IF EXISTS `item_images`, `images`;
Query OK, 0 rows affected (0.09 sec)
mysql> CREATE TABLE IF NOT EXISTS `images` (
-> `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
-> );
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE IF NOT EXISTS `item_images` (
-> `item_id` BIGINT UNSIGNED NOT NULL,
-> `image_id` BIGINT UNSIGNED NOT NULL
-> );
Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO `images`
-> VALUES (NULL), (NULL), (NULL),
-> (NULL), (NULL), (NULL);
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> INSERT INTO `item_images`
-> (`item_id`, `image_id`)
-> VALUES (1, 5), (1, 6), (2, 1),
-> (2, 3), (3, 2), (4, 2);
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql> SELECT `image_id`
-> FROM `item_images`
-> WHERE `item_id` = 1;
+----------+
| image_id |
+----------+
| 5 |
| 6 |
+----------+
2 rows in set (0.00 sec)
mysql> DELETE
-> FROM `images`
-> WHERE `id` IN (SELECT `image_id`
-> FROM `item_images`
-> WHERE `item_id` = 1);
ERROR 1175 (HY000): You are using safe update mode and you tried to update
a table without a WHERE that uses a KEY column
mysql> DELETE
-> FROM `images`
-> WHERE `id` > 0 AND
-> `id` IN (SELECT `image_id`
-> FROM `item_images`
-> WHERE `item_id` = 1);
Query OK, 2 rows affected (0.01 sec)
See db-fiddle.
UPDATE
In the first DELETE the index (key) is not reached.
mysql> SET SESSION SQL_SAFE_UPDATES := 0;
Query OK, 0 rows affected (0.00 sec)
mysql> EXPLAIN DELETE
-> FROM `images`
-> WHERE `id` IN (SELECT `image_id`
-> FROM `item_images`
-> WHERE `item_id` = 1);
+----+--------------------+-------------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+--------------------+-------------+------------+------+---------------+------+---------+------+------+----------+-------------+
| 1 | DELETE | images | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 100.00 | Using where |
| 2 | DEPENDENT SUBQUERY | item_images | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 16.67 | Using where |
+----+--------------------+-------------+------------+------+---------------+------+---------+------+------+----------+-------------+
2 rows in set (0.00 sec)
mysql> EXPLAIN DELETE
-> FROM `images`
-> WHERE `id` > 0 AND
-> `id` IN (SELECT `image_id`
-> FROM `item_images`
-> WHERE `item_id` = 1);
+----+--------------------+-------------+------------+-------+---------------+---------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+--------------------+-------------+------------+-------+---------------+---------+---------+-------+------+----------+-------------+
| 1 | DELETE | images | NULL | range | PRIMARY | PRIMARY | 8 | const | 6 | 100.00 | Using where |
| 2 | DEPENDENT SUBQUERY | item_images | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 16.67 | Using where |
+----+--------------------+-------------+------------+-------+---------------+---------+---------+-------+------+----------+-------------+
2 rows in set (0.01 sec)
See db-fiddle.