从多个表中选择计数并分组

Question

帮帮我！

$sql = SELECT `id`, `email`, `avatar`,`fullname`,
            SUM(result) as sum_result,
            SUM(total) as sum_total,
            COUNT(rank)  as `top_1` where `itq_exam_thread_test`.`rank` = 1, 
            COUNT(rank)  as `top_2` where `itq_exam_thread_test`.`rank` = 2,
            COUNT(rank)  as `top_3` where `itq_exam_thread_test`.`rank` = 3
GROUP BY userid_created
ORDER BY sum_result DESC, sum_rate DESC
LIMIT 0, 100';

您的 SQL 语法有错误；查看与您的 MariaDB 服务器版本相对应的手册，了解在 'where itq_exam_thread_test.rank = 1,

附近使用的正确语法

Answer 1

WHERE 是整个查询的子句，而不是SELECT 子句中的修饰符。你想要的是条件聚合。在 MySQL 中，进行计数非常容易，因为它将布尔表达式视为数字上下文中的整数。所以，你可以使用SUM():

SELECT id, email, avatar, fullname, SUM(result) as sum_result,
       SUM(total) as sum_total,
       SUM(rank = 1) as top_1,
       SUM(rank = 2) as top_2,
       SUM(rank = 3) as top_3
FROM itq_exam_thread_test
GROUP BY userid_created
ORDER BY sum_result DESC
LIMIT 0, 100;

我从ORDER BY 中删除了sum_rate，因为它没有定义。