Laravel Migration: Add a column with a default value of an existing column

Question

i need to add a last_activity column on a table of a live site where i have to make it's default value to equal of updated_at column value. I'm using laravel 5.1 and mysql database driver.

Schema::table('users', function(Blueprint $table)
{
    $table->dateTime('last_activity')->default("COLUMN VALUE OF UPDATED_AT");
});

Thanks.

tptcat · Accepted Answer · 2016-09-16 22:51:00Z

53

This should work:

Schema::table('users', function(Blueprint $table) {
    $table->dateTime('last_activity');
});

\DB::statement('UPDATE users SET last_activity = updated_at');

See "Running a General Statement": https://laravel.com/docs/5.1/database#database-transactions

To enforce this relationship when a User is created or updated, you can use Model Events and/or Model Observers.

edited Sep 16, 2016 at 22:51

answered May 12, 2016 at 11:14

tptcat

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2 Comments

Ben Swinburne Over a year ago

If you use $table->timestamp('last_activity')->useCurrent(); it'd continue to set last_activity whenever the row is updated.

DavidsKanal Over a year ago

Am I somehow missing the obvious here? This code fails if you have at least one row in users! You'll need to first create the column nullably, then set the defaults, and then disable the nullability.

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