How To Drop And Change Some Table In Chapter 4-5

I am new in YII, i just follow some tutorial and I want to drop one table and change some content. here is my first code :

public function safeUp()

{

    //create the issue table

    $this->createTable('tbl_issue', array(

        'id' => 'pk',

        'name' => 'string NOT NULL',

        'description' => 'text',

        'project_id' => 'int(11) DEFAULT NULL',

        'type_id' => 'int(11) DEFAULT NULL',

        'status_id' => 'int(11) DEFAULT NULL',

        'owner_id' => 'int(11) DEFAULT NULL',

        'requester_id' => 'int(11) DEFAULT NULL',

        'create_time' => 'datetime DEFAULT NULL',

        'create_user_id' => 'int(11) DEFAULT NULL',

        'update_time' => 'datetime DEFAULT NULL',

        'update_user_id' => 'int(11) DEFAULT NULL',

    ), 'ENGINE=InnoDB');


    //create the user table

    $this->createTable('tbl_user', array(

        'id' => 'pk',

        'username' => 'string NOT NULL',

        'email' => 'string NOT NULL',

        'password' => 'string NOT NULL',

        'last_login_time' => 'datetime DEFAULT NULL',

        'create_time' => 'datetime DEFAULT NULL',

        'create_user_id' => 'int(11) DEFAULT NULL',

        'update_time' => 'datetime DEFAULT NULL',

        'update_user_id' => 'int(11) DEFAULT NULL',

    ), 'ENGINE=InnoDB');


    //create the assignment table that allows for many-to-many relationship between projects and users

    $this->createTable('tbl_project_user_assignment', array(

        'project_id' => 'int(11) NOT NULL',

        'user_id' => 'int(11) NOT NULL',

        'PRIMARY KEY (`project_id`,`user_id`)',

    ), 'ENGINE=InnoDB');


    //foreign key relationships


    //the tbl_issue.project_id is a reference to tbl_project.id

    $this->addForeignKey("fk_issue_project", "tbl_issue", "project_id", "tbl_project", "id", "CASCADE", "RESTRICT");


    //the tbl_issue.owner_id is a reference to tbl_user.id

    $this->addForeignKey("fk_issue_owner", "tbl_issue", "owner_id", "tbl_user", "id", "CASCADE", "RESTRICT");


    //the tbl_issue.requester_id is a reference to tbl_user.id

    $this->addForeignKey("fk_issue_requester", "tbl_issue", "requester_id", "tbl_user", "id", "CASCADE", "RESTRICT");


    //the tbl_project_user_assignment.project_id is a reference to tbl_project.id

    $this->addForeignKey("fk_project_user", "tbl_project_user_assignment", "project_id", "tbl_project", "id", "CASCADE", "RESTRICT");


    //the tbl_project_user_assignment.user_id is a reference to tbl_user.id

    $this->addForeignKey("fk_user_project", "tbl_project_user_assignment", "user_id", "tbl_user", "id", "CASCADE", "RESTRICT");

}


public function safeDown()

{

    $this->truncateTable('tbl_project_user_assignment');

    $this->truncateTable('tbl_issue');

    $this->truncateTable('tbl_user');

    $this->dropTable('tbl_project_user_assignment');

    $this->dropTable('tbl_issue');

    $this->dropTable('tbl_user');

}

first, I want to drop table tbl_project in different migration file…

-the code above have migration file name: m140429_062423_create_issue_user_and_assignment_tables.php

-the migration file name that have table tbl_project is m140416_105213_create_project_table.php

second,I want to drop table tbl_project_user_assignment and delete some content in other tables like project_id… ofcourse i want to remove the foreign releation with project_id too…

How do i do that? what migrate command i must use? thx before…