Question

如果未找到第二个表行，如何显示第一行请参见示例感谢

$result1 = mysql_query("
SELECT a.user_name
     , a.date
     , a.checkin
     , o.checkout
  FROM attend a
  LEFT
  JOIN attendout o
    ON a.user_name = o.user_name 
   AND a.date = o.date
 WHERE a.date BETWEEN '2015-06-01' AND '2015-06-09' 
   AND o.user_name = 'salman';
");

现在显示如下

username   date      checkin    checkout
salman  2015-06-01  11:31:34    17:23:47
salman  2015-06-02  11:19:23    17:15:15
salman  2015-06-03  11:48:22    18:16:27
salman  2015-06-06  11:39:26    16:56:13
salman  2015-06-07  11:24:59    17:36:01

我想要这样

   username   date      checkin    checkout
    salman  2015-06-01  11:31:34    17:23:47
    salman  2015-06-02  11:19:23    17:15:15
    salman  2015-06-03  11:48:22    18:16:27
    salman  2015-06-06  11:39:26    16:56:13
    salman  2015-06-07  11:24:59    17:36:01
    salman  2015-06-08  12:24:59
    salman  2015-06-09  10:24:59

因为某些时间结帐行为空

Answer 1

将 second 表格中的条件从WHERE移至ON：

SELECT a.user_name, a.date, a.checkin, o.checkout
FROM attend a LEFT JOIN
     attendout o
     ON a.user_name = o.user_name AND
        a.date = o.date AND  o.user_name = 'salman'
WHERE a.date BETWEEN '2015-06-01' AND '2015-06-09' ;

当您将条件放在WHERE子句中时，您将LEFT JOIN变为INNER JOIN，因为NULL值被滤除了。

Answer 2

为结帐列添加条件：

SELECT attend.user_name,attend.date,attend.checkin, attendout.checkout
FROM attend 
left join  attendout on attend.user_name=attendout.user_name AND attend.date=attendout.date
WHERE attend.date BETWEEN '2015-06-01' 
AND '2015-06-09' 
AND attendout.user_name='salman'
AND attendout.checkout IS NOT NULL

或使用！=运算符，如果值可以为空

完整代码：如果你没有任何记录，将LEFT JOIN替换为INNER JOIN将对你有用

$result1 = mysql_query("
SELECT a.user_name
     , a.date
     , a.checkin
     , o.checkout
  FROM attend a
  JOIN attendout o
    ON a.user_name = o.user_name 
   AND a.date = o.date
 WHERE a.date BETWEEN '2015-06-01' AND '2015-06-09' 
   AND o.user_name = 'salman';
");

否则使用：

$result1 = mysql_query("
SELECT a.user_name
     , a.date
     , a.checkin
     , o.checkout
  FROM attend a
  LEFT JOIN attendout o
    ON a.user_name = o.user_name 
   AND a.date = o.date
 WHERE a.date BETWEEN '2015-06-01' AND '2015-06-09' 
   AND o.user_name = 'salman'
   AND o.checkout != ''
   AND o.checkout IS NOT NULL;
");

如果找不到第二个表行，如何显示第一行

2 个答案: