mysql随机获取优化话语

mysql随机获取优化语句
在网上找了一个随机取数语句，结合了自己的需求，运行出错，
看了半天没发现出错的地方，求指点

$str="select * from dizhi where shijiancuo>'$times' GROUP BY user HAVING COUNT(user) > 4 AS t1 

JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2 

WHERE t1.id >= t2.id 

ORDER BY t1.id ASC LIMIT 1" ;

select * from
(select * from dizhi where shijiancuo>'$times' GROUP BY user HAVING COUNT(user) > 4) AS t1
JOIN
(SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2
WHERE t1.id >= t2.id
ORDER BY t1.id ASC LIMIT 1