Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in D:\www\AppServ\www\tuijianshuchu.php on line 23 23代码如下$result=mysql_query($str, $con); //送出查詢 $rows=mysql_num_rows($result); //23行
$result=mysql_query($str, $con) or die(mysql_error());
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2 ' at line 1
select * from (select * from dizhi where shijiancuo>'$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
JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id from dizhi) AS t2
8楼的不行,7楼的OK,多谢了 一直没搞明白这句的意思 (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2 网上说ROUND 函数用于把数值字段舍入为指定的小数位数,所以不太理解这语句的结果是什么
RAND 产生一个小于 1 的随机数 SELECT MAX(id) FROM dizhi 取得表 dizhi 中最大的 id 值 ROUND 四舍五入化为整数这个查询指令的意思是: 任取表中的一个 id 值
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2 ' at line 1
(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
一直没搞明白这句的意思 (SELECT ROUND(RAND() * (SELECT MAX(id) FROM dizhi)) AS id) AS t2 网上说ROUND 函数用于把数值字段舍入为指定的小数位数,所以不太理解这语句的结果是什么
SELECT MAX(id) FROM dizhi 取得表 dizhi 中最大的 id 值
ROUND 四舍五入化为整数这个查询指令的意思是:
任取表中的一个 id 值