mysql查询和php - 如何实现这个？

问题描述：

Okay, so I have a table, with 20 fields named q1, q2, q3 all the way to q20

These fields contain answers, which is a number out of 10.

I want to basically choose 10 questions at random, and do some maths and the php to display it on page.

Here is what I have so far:

$selector = "10218";
/* Work out how many rows to divide by */
$nr = mysql_query("SELECT * FROM `reviews` WHERE `selector` = '" . $selector . "'");
$nr = mysql_num_rows($nr);
/* Get the total sum of answers for question 1  */
$q1 = mysql_query("SELECT sum(`q1`) AS `sum` FROM `reviews` WHERE `selector` = '" . $selector. "'");
$q1 = mysql_fetch_array($q1);
$q1 = $q1['sum'] / $nr;
echo "q1 avg is " . round($q1);

Basically, we want to do this for 10 questions - at random.

We don't want to have to write this code out 20 times, as it is quite strenuous and we want to do some sort of "array" to contain the questions in, and then a for each loop to loop 10 times with a random question?

We want to end up with:

q1 avg is 8
q2 avg is 4
q9 avg is 7
q4 avg is 8
q14 avg is 4
q18 avg is 6
q12 avg is 3
q7 avg is 10
q20 avg is 8
q13 avg is 9

How can we go about doing this? If you didn't understand let me know and I'll try rephrase it.

好的，所以我有一个表，有20个字段，名为q1，q2，q3，一直到 q20 code> p>

这些字段包含答案，这是10个数字。 p>


我想基本上随机选择10个问题， 并做一些数学和PHP在页面上显示它。 p> 
 
 
这是我到目前为止： p> 
 
 
  $ selector =“  10218“; 
 / *计算除以* / n $ nr = mysql_query（”SELECT * FROM`views` WHERE`selector` ='“。$ selector。”'“）; 
 $  nr = mysql_num_rows（$ nr）; 
 / *获取问题1的答案总和* / 
 $ q1 = mysql_query（“SELECT sum（`q1`）AS`sum` FROM`views` WHERE`selector`  ='“。$ selector。”'“）; 
 $ q1 = mysql_fetch_array（$ q1）; 
 $ q1 = $ q1 ['sum'] / $ nr; 
echo”q1 avg is“。  round（$ q1）; 
  code>  pre> 
 
 基本上，我们想要随机执行10个问题。 p> 
 
 
我们不要 我不想写这个代码20次，因为它非常费劲，我们想做某种“数组”来包含问题，然后用一个随机问题循环10次循环？   p> 
 
 
我们希望最终得到： p> 
 
 
  q1 avg is 8 
q2 avg is 4 
q9 avg is 7 
q4 avg is  8 
q14平均值为4 
q18平均值为6 
q12平均值为3 
q7平均值为10 
q20平均值为8 
q13平均值为9 
  code>  pre> 
 
 怎么能 我们去做这个？ 如果您不理解，请告诉我，我会尝试改写它。 p> 
  div>

答

How about this:

// ...
$query = 'SELECT';
for ( $i = 1; $i <= 20; $i ++ ) {
    $query .= ' SUM(`q' . $i . '`) AS `sum' . $i . '`';
}
$query .= 'FROM `reviews` WHERE `selector` = "' . $selector . '"';

$q1 = mysql_query( $query );
$q1 = mysql_fetch_array( $q1 );
foreach ( array_rand( $q1, 10 ) as $col => $sum ) {
    echo $col . ' is ' . $sum . '<br />';
}

By the way, the sum is not the average :)

答

I don't think what you are trying to do is very clear.

I think you can get the average response as follows:

SELECT AVG(q1) FROM `reviews` WHERE `selector` = $selector;

As suggested in the above comments, you may be better with a a database that looks like this:

create table reviews (
selector ???,
question integer not null, /* e.g. 1, 2, 3, up to 20 */
answer integer not null);

Then you could do something like

SELECT question, avg(answer)
FROM reviews
WHERE selector = $selector
GROUP BY selector
ORDER BY rand()
LIMIT 10;

Though I am not sure of the role of 'selector', and suspect it is bogus.

mysql查询和php - 如何实现这个？

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