Question

我已经有了一个表名table_one.，现在我想再添加两个列。到目前为止一切正常。但是在我的方法中，我想检查表中是否存在像dropIfExists('table').

这样的列

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    Schema::table('table_one', function (Blueprint $table) {
        $table->string('column_one')->nullable();
        $table->string('column_two')->nullable();
    });
}

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::table('table_one', function (Blueprint $table) {
        // in here i want to check column_one and column_two exists or not
        $table->dropColumn('column_one');
        $table->dropColumn('column_two');
    });
}

Answer 1

您需要像这样的东西

  public function down()
    {
        if (Schema::hasColumn('users', 'phone'))
        {
            Schema::table('users', function (Blueprint $table)
            {
                $table->dropColumn('phone');
            });
        }
    }

Answer 2

您可以创建自己的“dropColumnIfExists()”函数来检查列是否存在，然后将其删除：

function myDropColumnIfExists($myTable, $column)
{
    if (Schema::hasColumn($myTable, $column)) //check the column
    {
        Schema::table($myTable, function (Blueprint $table)
        {
            $table->dropColumn($column); //drop it
        });
    }

}

并在“down()”函数上使用它，如下所示：

public function down()
{
    myDropColumnIfExists('table_one', 'column_two');
    myDropColumnIfExists('table_one', 'column_one');
}

Answer 3

只需将架构分为两个调用

public function up()
{
    Schema::table('table_one', function (Blueprint $table) {
        $table->dropColumn(['column_one', 'column_two']);
    });

    Schema::table('table_one', function (Blueprint $table) {
        $table->string('column_one')->nullable();
        $table->string('column_two')->nullable();
    });
}

检查Laravel迁移文件中是否存在列

3 个答案: