Question

我有一个投票系统，表格如下：

answers
-----------
int id
text content

results
-----------
int id
int answers_id

我想要一个选择，所以即使没有投票（结果），我也可以看到答案和回复的数量。我试过这样的事情：

SELECT 
count(results.answers_id), answers.content
from answers
left outer join results
on answers.id = results.answers_id
group by results.answers_id

但它没有以0票（结果）得到答案。

Answer 1

尝试

SELECT
count(result.answers_id) as acount, answers.content
from answers
left inner join results
on answers.id = acount

Answer 2

使用子查询

SELECT a.*,
   ( SELECT COUNT(*)
     FROM results r
     WHERE a.id = r.answers_id
   )
FROM answers a

Answer 3

试试这个，按答案的ID分组。

SELECT 
COUNT(results.answers_id) AS NumberOfAnswers, answers.content
from answers
left join results
on answers.id = results.answers_id
group by answers.id

为了确保您没有2行具有相同内容，请group by answers.content

    SELECT 
    COUNT(results.answers_id) AS NumberOfAnswers, answers.content
    from answers
    left join results
    on answers.id = results.answers_id
    group by answers.content

Answer 4

使用Ifnull并在您的分组语句中将其更改为answers.content

SELECT 
IFNULL(count(results.answers_id),0), answers.content
from answers
left outer join results
on answers.id = results.answers_id
group by answers.content

Answer 5

我认为解决方案是使用IFNULL

SELECT IFNULL(COUNT(r.answers_id), 0), 
       a.content
FROM   answers AS a
LEFT JOIN results AS r ON a.id = r.answers_id
GROUP BY r.answers_id

Answer 6

这应该做的工作：

SELECT count(results.answer_id), answers.content
from answers left outer join results on answers.id = results.answer_id
group by answers.content;

mySQL投票系统SELECT

6 个答案: