mysql - 如果值为空，则忽略条件MYSQL/Codeigniter

我正在使用MYSQL / Codeigniter。如果传递的值为空，MySQL查询如何忽略条件，例如以下示例：

function get_category($category_id = 0){

 return $this->db->query("SELECT * FROM {$this->table} c
                    INNER JOIN db_category_event ce
                    ON ce.category_id = c.category_id
                    INNER JOIN db_event_type e
                    ON e.event_id = ce.event_id
                     WHERE c.category_id = {$category_id}
                    WHERE c.visible = 1 AND e.visible = 1")
            ->result();
  }

最佳答案

尝试这个：

SELECT *

FROM   {$this->table} c

       INNER JOIN db_category_event ce
       ON ce.category_id = c.category_id

       INNER JOIN db_event_type e
       ON e.event_id = ce.event_id

WHERE   ({$category_id} IS NULL OR c.category_id = {$category_id})
        AND c.visible = 1 AND e.visible = 1

或者，如果参数被视为零，则应该可以使用：

SELECT *

FROM   {$this->table} c

       INNER JOIN db_category_event ce
       ON ce.category_id = c.category_id

       INNER JOIN db_event_type e
       ON e.event_id = ce.event_id

WHERE   ({$category_id} = 0 OR c.category_id = {$category_id})
        AND c.visible = 1 AND e.visible = 1

关于mysql - 如果值为空，则忽略条件MYSQL/Codeigniter，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/14730627/