Question

我正在尝试使用其中一个高级随机函数从mysql数据库中获取一行。但是，当我尝试过滤以仅获取其中包含“field = 1”的行时，一切都会失败。有人可以发现我的错误吗？

SELECT username, message, ttime 
FROM table WHERE done LIKE '1' AS r1 JOIN 
   (SELECT (RAND() *
                 (SELECT MAX(id)
                    FROM database)) AS id)
    AS r2
WHERE r1.id >= r2.id
ORDER BY r1.id ASC
LIMIT 1;";

Answer 1

您的问题中的查询有多个语法错误。你想要这样的东西吗？

SELECT username, message, ttime 
FROM database.table1 as r1 
INNER JOIN 
   (SELECT (RAND() * MAX(id)) as a_random_id
    FROM database.table1) r2
ON (r1.id >= r2.a_random_id)
WHERE done = '1'
ORDER BY r1.id ASC
LIMIT 1

我想知道这种变体是否更快：

SELECT r.username, r.message, r.ttime 
FROM database.table1 r 
WHERE r.id = (  
  SELECT MIN(r1.id)  <<-- this should make MySQL stop after the first hit.
  FROM database.table1 r1 
  INNER JOIN 
     (SELECT (RAND() * MAX(id)) as a_random_id
      FROM database.table1) AS r2
  ON (r1.id >= r2.a_random_id)
  WHERE r1.done = '1') sub

哦，你没有从database中选择，你从数据库中的 table 中选择。

随机获取字段不在的行，mysql

1 个答案: