How can I set the default value of a timestamp col

问题:

I would like to make a timestamp column with a default value of CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP using the Laravel Schema Builder/Migrations. I have gone through the Laravel documentation several times and I don't see how I can make that the default for a timestamp column.

The timestamps() function makes the defaults 0000-00-00 00:00 for both columns that it makes.

回答1:

Since it's a raw expression, you should use DB::raw() to set CURRENT_TIMESTAMP as a default value for a column:

$table->timestamp('created_at')->default(DB::raw('CURRENT_TIMESTAMP'));

This works flawlessly on every database driver.

As of Laravel 5.1.25 (see PR 10962 and commit 15c487fe) you can use the new useCurrent() column modifier method to set the CURRENT_TIMESTAMP as a default value for a column:

$table->timestamp('created_at')->useCurrent();

As asked, on MySQL you could also use the ON UPDATE clause through DB::raw():

$table->timestamp('updated_at')->default(DB::raw('CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP'));

Gotchas

• MySQL
  
  Starting with MySQL 5.7, 0000-00-00 00:00:00 is no longer considered a valid date. As documented at the Laravel 5.2 upgrade guide, all timestamp columns should receive a valid default value when you insert records into your database. You may use the useCurrent() column modifier (from Laravel 5.1.25 and above) in your migrations to default the timestamp columns to the current timestamps, or you may make the timestamps nullable() to allow null values.

• PostgreSQL & Laravel 4.x
  
  In Laravel 4.x versions, the PostgreSQL driver was using the default database precision to store timestamp values. When using the CURRENT_TIMESTAMP function on a column with a default precision, PostgreSQL generates a timestamp with the higher precision available, thus generating a timestamp with a fractional second part - see this SQL fiddle.

  This will led Carbon to fail parsing a timestamp since it won't be expecting microseconds being stored. To avoid this unexpected behavior breaking your application you have to explicitly give a zero precision to the CURRENT_TIMESTAMP function as below:

  $table->timestamp('created_at')->default(DB::raw('CURRENT_TIMESTAMP(0)'));
  

  Since Laravel 5.0, timestamp() columns has been changed to use a default precision of zero which avoids this.

  Thanks to @andrewhl for pointing out this issue in the comments.

回答2:

To create both of the created_at and updated_at columns:

$t->timestamp('created_at')->default(DB::raw('CURRENT_TIMESTAMP'));
$t->timestamp('updated_at')->default(DB::raw('CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP'));

You will need MySQL version >= 5.6.5 to have multiple columns with CURRENT_TIMESTAMP

回答3:

Starting from Laravel 5.1.26, tagged on 2015-12-02, a useCurrent() modifier has been added:

Schema::table('users', function ($table) {
    $table->timestamp('created')->useCurrent();
});

PR 10962 (followed by commit 15c487fe) leaded to this addition.

You may also want to read issues 3602 and 11518 which are of interest.

Basically, MySQL 5.7 (with default config) requires you to define either a default value or nullable for time fields.

回答4:

Use Paulo Freitas suggestion instead.

---

Until Laravel fixes this, you can run a standard database query after the Schema::create have been run.

    Schema::create("users", function($table){
        $table->increments('id');
        $table->string('email', 255);
        $table->string('given_name', 100);
        $table->string('family_name', 100);
        $table->timestamp('joined');
        $table->enum('gender', ['male', 'female', 'unisex'])->default('unisex');
        $table->string('timezone', 30)->default('UTC');
        $table->text('about');
    });
    DB::statement("ALTER TABLE ".DB::getTablePrefix()."users CHANGE joined joined TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL");

It worked wonders for me.

回答5:

This doesn't work for a fact:

$table->timestamp('created_at')->default('CURRENT_TIMESTAMP');

It doesn't remove the 'default 0' that seems to come with selecting timestamp and it just appends the custom default. But we kind of need it without the quotes. Not everything that manipulates a DB is coming from Laravel4. That's his point. He wants custom defaults on certain columns like:

$table->timestamps()->default('CURRENT_TIMESTAMP');

I don't think it's possible with Laravel. I've been searching for an hour now to see whether it's possible.

---

Update: Paulos Freita's answer shows that it is possible, but the syntax isn't straightforward.

回答6:

In Laravel 5 simply:

$table->timestamps(); //Adds created_at and updated_at columns.

Documentation: http://laravel.com/docs/5.1/migrations#creating-columns

回答7:

This is how you do it, I have checked it and it works on my Laravel 4.2.

$table->timestamp('created_at')->default(DB::raw('CURRENT_TIMESTAMP'));

Hope this helps.

回答8:

Usethe following:

$table->timestamp('created_at')->nullable();

Hopefully, it will help you. Thank you.