laravel Attach vs Sync difference.

attach():

• Insert related models when working with many-to-many relations
• No array parameter is expected

Example:

$user = User::find(1);

$user->roles()->attach(1);

sync()

Similar to the attach() method. sync() also use to attach related models. However main difference is:

• Sync method accepts an array of IDs to place on the pivot table
• Secondly, most important, The sync method will delete the models from table if model does not exist in array and insert new items to the pivot table.

Example:

user_role

id  user_id role_id
1    12       1
2    12       5
3    12       2

$user = User::find(12);
$user->roles()->sync(array(1, 2, 3));

The above operation will delete:

id  user_id role_id
2    12       5

And insert role_id 3 to the table.

user_role table

id  user_id role_id
1    12       1
3    12       2
4    12       3

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edited Aug 21 at 1:31

Gazzer

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answered May 31 '14 at 12:06

Anam

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• 14
  Thank you! So in theory, using $user()->roles()->detach($oldIDs) followed by $user()->roles()->attach($newIDs) is the same as $user()->roles()->sync($newIDs), right? – Kousha May 31 '14 at 23:25
• 20
  Also there is one second argument for sync() that is by default true, if you pass false, then the non matching will not be deleted. Refer: laravel.com/api/4.2/Illuminate/Database/Eloquent/Relations/… – Musa Haidari Dec 18 '14 at 6:24
• get last insert id in sync? – Deenadhay