Laravel Eloquent created_at正在更新

Question

I just hit a snag with Eloquent's (Laravel 5.2.10) default timestamps. By default the $table->timestamps() method gives you a created_at and an updated_at column in your table which are updated accordingly.

However, when I was trying some test entries, I noticed that when you update a record, the updated_at field gets updated, as it should, but the created_at field also gets updated: its hours stays at the created time, but the minutes and seconds get updated to match the updated_at field.

If that was too wordy, here is an example:

+---------------------+---------------------+
| created_at          | updated_at          |
+---------------------+---------------------+
| 2016-01-13 17:13:27 | 2016-01-13 22:13:27 |
| 2016-01-13 16:14:41 | 2016-01-13 21:14:41 |
+---------------------+---------------------+

Notice that the minutes and seconds are the exact same for the created_at and updated_at field.

I tried to look through the Model class where the timestamps are set, but it turns out the setCreatedAt() method is indeed not called when just updating a record.

Why does this happen?
How do I prevent the created_at field from changing? (more important)

Answer 1

Your issue is probably related to this issue here: https://github.com/laravel/framework/issues/11518

Long story short, many people's created_at column had the ON UPDATE CURRENT_TIMESTAMP attribute.

As stated on the Github page:

MySQL 5.7 no longer allows 0000-00-00 as a valid timestamp with strict mode turned on (which it is by default). So either use ->nullableTimestamps() or ->timestamp()->useCurrent().

So, you can fix this by changing this:

$table->timestamps();

To either one of these options:

// Option 1:
$table->nullableTimestamps();

// Option 2:
$table->timestamp('updated_at')->useCurrent();
$table->timestamp('created_at')->useCurrent();

Also, on this MySQL page: https://dev.mysql.com/doc/refman/5.6/en/timestamp-initialization.html

Alternatively, if explicit_defaults_for_timestamp is disabled (the default), do either of the following:

Define the column with a DEFAULT clause that specifies a constant default value.

Specify the NULL attribute. This also causes the column to permit NULL values, which means that you cannot assign the current timestamp by setting the column to NULL. Assigning NULL sets the column to NULL.