MySQL Update Query using a left join

Question

Table Schema

Table Name: file_manager_folder

Rows: id , parentId, name

My query

Answer 1

So you want to move folders only if a folder of the same name under the target parent folder does not exist:

UPDATE file_manager_folder f1
LEFT OUTER JOIN file_manager_folder f2 
    ON f1.name = f2.name AND f2.parentId = 54
SET f1.parentId = 54 
WHERE f2.name IS NULL AND f1.id IN (1,2,3);

The join condition searches for a folder with the same name under the target parent. The WHERE clause tests that no such folder exists (f2.name is null only if the outer join finds no match).