问题
Basically this is a survey system and I want to count the Yes's and No's from my results table which has
| q1 | q2 | q3 | q4 | q5 | q6 | q7 | q8 | q9 | q10 |
| Yes | Yes | No | No | No | Yes | No | Yes | Yes | No |
| No | Yes | No | Yes | Yes | Yes | No | No | Yes | No |
| Yes | Yes | No | No | No | Yes | No | Yes | Yes | No |
| No | Yes | No | Yes | Yes | Yes | No | No | Yes | No |
For example I want my result to be q1 = 2 No's 2 Yes and q2 = 4 yes 0 No's and so on Then after that I was hoping to display it in a simple table but I'm still clueless about the query
<body>
<form method="POST">
<table border="1">
<th>Answered Yes</th>
<th>Answered No</th>
</tr>
<?php
include("testdb.php");
$result= mysqli_query($con, "SELECT * FROM results");
if($result){
?>
</table>
</body>
回答1:
Just use boolean expressions:
select ((q1 = 'Yes') + (q2 = 'Yes') + . . . + (q10 = 'Yes')) as numYes
MySQL treats a conditional expression as a number in a numeric context, with 1 for true and 0 for false.
回答2:
In MySQL (only) true is 1 and false is 0, so summing a condition counts how many times it's true:
select
sum((q1 = 'Yes') + (q2 = 'Yes') + ... etc) yeses,
sum((q1 = 'No') + (q2 = 'No') + ... etc) nod
from mytable
来源：https://stackoverflow.com/questions/41538841/selecting-and-displaying-the-count-of-rows-with-the-same-value-in-a-table