Question

我有一个查询按月和年计算所有工作ID号，然后使用jpgraph创建过去13个月的图表。除非7月份没有工作ID号码，否则它的效果很好，因此图表完全会跳过7月份。

查询结果：

期望的结果：

正如您所看到的，我需要（0）零才能使我的图表正常工作，但是由于7月份没有工作ID号，我的查询只是跳过它。这是我的疑问：

SELECT COUNT( WORK_ID_NUM ) AS count, 
DATE FROM SERVICE_JOBS 
WHERE (DATE BETWEEN '$lastyear' AND '$date') 
AND JOB_TYPE LIKE 'Street Light' 
GROUP BY YEAR( DATE ), MONTH( DATE )
 ORDER BY DATE

Answer 1

要让您的查询返回7月份的行，您需要在其中添加包含7月的行。你可以创建一个表格，其中包含$ lastyear和$ date之间的所有日期，然后从那里连接到SERVICE_JOB。

SELECT COUNT( WORK_ID_NUM ) AS count, 
       allDates.DATE 
FROM AllDates 
Left outer join SERVICE_JOB
on AllDates.DATE = SERVICE_JOB.DATE
WHERE (AllDates.DATE BETWEEN '$lastyear' AND '$date') AND
(SERVICE_JOB.WORK_ID_NUM is NULL OR JOB_TYPE LIKE 'Street Light')
GROUP BY YEAR( AllDates.DATE ), MONTH( AllDates.DATE ) 
ORDER BY AllDates.DATE

在SQL Server中，根据$ lastyear和$ date制作一个可以为你填充AllDates的Common Table Expression非常容易。不确定MySql。

Answer 2

sqlFiddle Demo

SELECT IFNULL(count,0) as count,theDate as Date
FROM 
      (SELECT @month := @month+INTERVAL 1 MONTH as theDate
       FROM service_jobs,(SELECT @month:='$lastyear' - INTERVAL 1 MONTH)as T1
       LIMIT 13)as T2
LEFT JOIN 
      (SELECT COUNT(WORK_ID_NUM)as count,DATE
       FROM service_jobs
       WHERE (DATE BETWEEN '$lastyear' AND '$date') 
         AND JOB_TYPE LIKE 'Street Light' 
       GROUP BY YEAR(DATE), MONTH(DATE)) T3
 ON (YEAR(theDate) = YEAR(DATE) AND MONTH(theDate) = MONTH(DATE))
ORDER BY theDate;

查询返回null而不是0

2 个答案: