system/Database/Forge.php
public function dropColumn(string $table, string $column_name)
	{
		$sql = $this->_alterTable('DROP', $this->db->DBPrefix . $table, $column_name);
		if ($sql === false)
		{
			if ($this->db->DBDebug)
			{
				throw new DatabaseException('This feature is not available for the database you are using.');
			}

			return false;
		}

		return $this->db->query($sql);
	}
public function dropColumn(string $table, string $column_name)
	{
		$sql = $this->_alterTable('DROP', $this->db->DBPrefix . $table, $column_name);
		if ($sql === false)
		{
			if ($this->db->DBDebug)
			{
				throw new DatabaseException('This feature is not available for the database you are using.');
			}

			return false;
		}

		return $this->db->query($sql);
	}
Column Drop

@param string $table       Table name
@param string $column_name Column name

@return mixed
@throws \CodeIgniter\Database\Exceptions\DatabaseException