MySQL的工作不IS NOT NULL

Question

所以我有以下查询

query = "SELECT date_format(startPeriod,'%a, %M, %d, %Y') as startDate, 
      date_format(startTime,'%I:%i%p') as startTime, 
      date_format(endTime,'%I:%i%p') as endTime, 
      jobLocation,jobId, 
       hoursWorked 
     FROM users,paycheck 
     WHERE users.userId = '" . $_SESSION['userId'] . 
     "' AND userId = empId 
     AND startPeriod IS NOT NULL 
     ORDER BY paycheck.startPeriod DESC"; 

的问题是，一些startPeriod的值（这是一个日期）为null所以，当我跑我的查询我不想以显示那些为空的日期，但不幸的是，日期是空的显示在我的表上。我怎样才能解决这个问题？

这是我的源

<tr><td></td><td>12:00AM</td><td>12:00AM</td><td>none</td><td>none</td><td>0.00</td></tr> 

我的输出文件的第一TDS之间，你可以看到它的空

Answer 1

你确定插入的数据实际上是空的，而不是只是一个空字符串？

之后更换startPeriod IS NOT NULL到TRIM(startPeriod) <> ""

OR

query = "SELECT date_format(startPeriod,'%a, %M, %d, %Y') as startDate, 
      date_format(startTime,'%I:%i%p') as startTime, 
      date_format(endTime,'%I:%i%p') as endTime, 
      jobLocation,jobId, 
       hoursWorked 
     FROM users,paycheck 
     WHERE users.userId = '" . $_SESSION['userId'] . 
     "' AND userId = empId 
     AND (startPeriod != '0000-00-00' OR startPeriod IS NOT NULL) 
     ORDER BY paycheck.startPeriod DESC"; 

这可能帮助你。