Php 如何将select嵌入select或从select调用另一个函数？

我有这样一个select语句：

    SELECT c.id AS courseid, u.id AS userid

    FROM

    mdl_user_enrolments ue
    join mdl_enrol e on e.id = ue.enrolid
    join mdl_user u on u.id = ue.userid
    join mdl_course c on c.id = e.courseid

        SELECT c.id AS courseid, u.id as userid,

             '.getLastCourseAccessByUser(c.id,u.id).' AS lastaccessdate

    FROM

        mdl_user_enrolments ue
        join mdl_enrol e on e.id = ue.enrolid
        join mdl_user u on u.id = ue.userid
        join mdl_course c on c.id = e.courseid

我还需要另一段数据，它与当前表没有直接关系。我一直在输出循环中调用这个函数

function getLastCourseAccessByUser($courseid, $userid){
global $DB;
return
    $DB->get_record_sql('
    SELECT FROM_UNIXTIME(time, "%m/%d/%Y") as ftime
    FROM mdl_log
    WHERE course = '.$courseid.' AND userid = '.$userid.'

    ORDER BY time DESC
    limit 1
');

}

但我宁愿一次获取所有数据，也不回叫数据库

我正在尝试：

            SELECT c.id AS courseid, u.id as userid

            (
               SELECT FROM_UNIXTIME(time, "%m/%d/%Y") as ftime
               FROM mdl_log
               WHERE course = c.id AND userid = u.id 
            )  AS lastaccessdate

        FROM

         mdl_user_enrolments ue
         join mdl_enrol e on e.id = ue.enrolid
         join mdl_user u on u.id = ue.userid
         join mdl_course c on c.id = e.courseid

或者，我可以直接从sql调用函数，如下所示：

    SELECT c.id AS courseid, u.id AS userid

    FROM

    mdl_user_enrolments ue
    join mdl_enrol e on e.id = ue.enrolid
    join mdl_user u on u.id = ue.userid
    join mdl_course c on c.id = e.courseid

        SELECT c.id AS courseid, u.id as userid,

             '.getLastCourseAccessByUser(c.id,u.id).' AS lastaccessdate

    FROM

        mdl_user_enrolments ue
        join mdl_enrol e on e.id = ue.enrolid
        join mdl_user u on u.id = ue.userid
        join mdl_course c on c.id = e.courseid

多谢各位

SELECT c.id AS courseid, u.id AS userid, FROM_UNIXTIME(t.time, "%m/%d/%Y") as ftime

    FROM

    mdl_user_enrolments ue
    join mdl_enrol e on e.id = ue.enrolid
    join mdl_user u on u.id = ue.userid
    join mdl_course c on c.id = e.courseid
    join mdl_log t on t.course = c.id and t.userid = u.id

您可以在mysql中的联接中放置AND和OR子句，以便可以在两个条件上联接。尽管您可能希望将其设置为外部联接，以便在不满足条件时不会使整个查询失败

否则，您的子选择选项也应起作用（此选项）

您可以在mysql中的联接中放置AND和OR子句，以便可以在两个条件上联接。尽管您可能希望将其设置为外部联接，以便在不满足条件时不会使整个查询失败

否则，您的子选择选项也应起作用（此选项）

---

在MySQL服务器端处理的数据越多，MySQL服务器和PHP应用程序之间产生的流量就越少，从而加快了应用程序的速度。我想说的是一次从服务器获取所有数据，不要来回太多次

如果需要在其他应用程序中重复使用，还可以在MySQL中创建

getLastCourseAccessByUser

函数作为存储函数：

DELIMITER \\
DROP FUNCTION IF EXISTS getLastCourseAccessByUser\\
CREATE FUNCTION getLastCourseAccessByUser (in_course_id INT, in_user_id VARCHAR(50) 
RETURNS STRING
BEGIN
    SELECT FROM_UNIXTIME(time, "%m/%d/%Y") AS ftime
    FROM mdl_log
    WHERE course = in_course_id AND userid = in_user_id 
    ORDER BY time DESC
    LIMIT 1
END\\
DELIMITER ;

然后您可以在

SELECT

语句中使用它：

SELECT c.id AS courseid, 
       u.id as userid,
       getLastCourseAccessByUser(c.id,u.id) AS lastaccessdate
  FROM mdl_user_enrolments ue
  JOIN mdl_enrol e on e.id = ue.enrolid
  JOIN mdl_user u on u.id = ue.userid
  JOIN mdl_course c on c.id = e.courseid

---

在MySQL服务器端处理的数据越多，MySQL服务器和PHP应用程序之间产生的流量就越少，从而加快了应用程序的速度。我想说的是一次从服务器获取所有数据，不要来回太多次

如果需要在其他应用程序中重复使用，还可以在MySQL中创建

getLastCourseAccessByUser

函数作为存储函数：

DELIMITER \\
DROP FUNCTION IF EXISTS getLastCourseAccessByUser\\
CREATE FUNCTION getLastCourseAccessByUser (in_course_id INT, in_user_id VARCHAR(50) 
RETURNS STRING
BEGIN
    SELECT FROM_UNIXTIME(time, "%m/%d/%Y") AS ftime
    FROM mdl_log
    WHERE course = in_course_id AND userid = in_user_id 
    ORDER BY time DESC
    LIMIT 1
END\\
DELIMITER ;

然后您可以在

SELECT

语句中使用它：

SELECT c.id AS courseid, 
       u.id as userid,
       getLastCourseAccessByUser(c.id,u.id) AS lastaccessdate
  FROM mdl_user_enrolments ue
  JOIN mdl_enrol e on e.id = ue.enrolid
  JOIN mdl_user u on u.id = ue.userid
  JOIN mdl_course c on c.id = e.courseid