Answers for "constraint delete and create new laravel migration"

laravel migration remove unique constraint

/** To drop an index you must specify the index's name. 
Laravel assigns a reasonable name to the indexes by default. 
Simply concatenate the table name, the names of the column in the index, 
and the index type **/

// Format of unique key tableName_column_unique
$table->dropUnique('users_email_unique');

table drop foreign php laravel

public function down()
 {
   Schema::table('tarefas', function (Blueprint $table) {
     $table->dropForeign('tarefas_user_id_foreign');

     $table->dropColumn('user_id');
   });
 }