Question

我有两张桌子

table_school

school_open_time|school_close_time|school_day
8:00 AM         | 9:00PM          | Monday
10:00 AM        | 7:00PM          | Wednesday

table_college

 college_open_time|college_close_time|college_day    
 10:00 AM         | 8:00PM           | Monday
 10:00 AM         | 9:00PM           | Tuesday
 10:00 AM         | 5:00PM           | Wednesday

现在我想根据今天（意味着school_open_time）选择school_close time college_open_time，college_close_time和college_day=school_day=today，以及如果没有排在任何一个表格中的特定日期，它会显示空白字段（LEFT JOIN，我想我可以使用）。

请为此建议我最佳和优化的查询。

更新

如果学校没有开放时间和休息时间，则必须返回college_open_time和college_close_time（不要填入数据库，只返回）作为school_open_time和school_close_time。并且在某一天必须有college_open_time和college_close_time

我使用以下查询

 SELECT college_open_time,college_close_time ,school_open_time,
        school_close_time  FROM tbl_college
 LEFT JOIN tbl_school ON school_owner_id=college_owner_id 
 WHERE college_owner_id='".$_session['user_id']."' AND
 college_day='".date('l',time())."'";

当table_school中没有给定日期的行时返回单行（左手有一些值，右手有空值），但是在左侧显示七行具有相同值的行（college_open_time，college_close_time）和6右侧的空白行（school_open_time和school_close_time）

i need only one row when both table have a row of a given day

但是使用上面的查询只占用相应table_school的第一行，其中school_owner_id是50（let），它没有看到应该给出school_day名称的条件

更多更新@ 37Stars

还有一点问题亲爱的， school_close_time和school_open时间的数据类型为TIME类型而college_open_time和college_close_time的数据类型为VARCHAR类型。我使用下面给出的代码，但我修改了一点，我接近结果，

但是现在告诉我在下面的代码段中我必须写下IFNULL

IFNULL（TIME_FORMAT（））或TIME_FORMAT（IFNULL（））

SELECT TC.owner_id,college_open_time AS collegeOpen, 
       college_close_time AS collegeClose, 
TIME_FORMAT(school_open_time, '%h:%i %p' ) AS schoolOpen,       
TIME_FORMAT(school_close_time, '%h:%i %p' ) AS schoolClose
FROM tbl_college TC
LEFT JOIN tbl_school  TS ON TS.owner_id = TC.owner_id
AND TC.college_day = TS.school_day
WHERE college_day = DATE_FORMAT(NOW(),'%W')

解决方案

感谢37stars，你是天才，但感谢IFNULL，

我写的是OPTIMUM AND BEST QUERY

SELECT TC.owner_id,college_open_time AS collegeOpen,college_close_time AS 
    collegeClose, IFNULL(TIME_FORMAT(school_open_time, '%h:%i %p'),college_open_time) 
    AS schoolOpen,IFNULL(TIME_FORMAT(school_close_time, '%h:%i %p',college_close_time)
    AS schoolClose FROM tbl_college TC LEFT JOIN tbl_school TS 
    ON TS.owner_id = TC.owner_id AND TC.college_day = TS.school_day 
    WHERE college_day = DATE_FORMAT(NOW(),'%W') 
    FROM tbl_storecalendar TS LEFT JOIN tbl_delivery_hours TD 
    ON TD.store_id = TS.store_id 
    AND TD.del_day = TS.dayName WHERE dayName = DATE_FORMAT( NOW( ) , '%W' )

Answer 1

你想要一个FULL OUTER JOIN，但遗憾的是MySQL不支持这个。幸运的是，使用UNION ALL组合左连接和右连接有一种解决方法：

更新：更改了查询以回答OP的更新问题。

SELECT
    COALESCE(school_day, college_day) AS day,
    COALESCE(school_open_time, college_open_time) AS school_open_time,
    COALESCE(school_close_time, college_close_time) AS school_close_time,
    COALESCE(college_open_time, school_open_time) AS college_open_time,
    COALESCE(college_close_time, school_close_time) AS college_close_time
FROM (
    SELECT * FROM table_school LEFT JOIN table_college ON school_day = college_day
    UNION ALL
    SELECT * FROM table_school RIGHT JOIN table_college ON school_day = college_day
    WHERE school_day IS NULL
) AS T1

Answer 2

我建议将数据库结构更改为具有以下结构的两个表：

table institutions: institution | institution_id table times: institution_id | day | open_time | close_time

您可以轻松地将两个现有表格放入新时间表，即
INSERT INTO times(institution, day, open_time, close_time) SELECT 'School', school_day, school_open_time, school_close_time FROM table_school

然后获取查询结果很简单：
SELECT i.institution, t.open_time, t.close_time FROM times t LEFT JOIN institutions i on t.institution_id=i.institution_id WHERE day='Wednesday'

Answer 3

如果您想在一个查询中完成此操作，则必须使用UNION将结果放在一起，如下所示：

SELECT school_open_time AS openTime,`int` AS school_close_time
    FROM table_school WHERE school_day=DATE_FORMAT(NOW(),'%W')
UNION
SELECT college_open_time AS openTime,`int` AS college_close_time
    FROM table_college WHERE college_day=DATE_FORMAT(NOW(),'%W');

DATE_FORMAT(NOW(),'%W')转换为当周的当天。

然而，这种方法对我来说似乎并不那么好。首先，在缺少记录的情况下，它不会处理将NULL方法放入结果集中。您可以添加一些IF / ELSE语句来为您完成此操作，但说实话，我可能只是从您的PHP代码中进行两次单独的查询。这样，您可以专门处理每一个并从那里更容易地控制您的结果。

Answer 4

您需要将 school_day = college_day 添加到您的JOIN子句中。

SELECT college_open_time, college_close_time, school_open_time, school_close_time
FROM dbo.tbl_college AS TC
    LEFT JOIN dbo.tbl_school AS TS ON TS.owner_id = TC.owner_id 
    AND TS.school_day = TC.college_day
WHERE TC.owner_id = 1 
    AND college_day = 'tuesday'

如何将两个表字段名称与mysql中的另一个值进行比较？

4 个答案: