Converting two loops to smarty - php

Question

I have two cycles in PHP, that I needed converting to smarty structure. Down includes PHP code.
Code:
<pre>
$query = mysqli_query($cnn, "SELECT *, COUNT(*) AS ph FROM course INNER JOIN completed_course ON course.id = completed_course.id_course GROUP BY course.id");
while ($row = mysqli_fetch_array($query)){
<tr> <td> <?php echo $row['id']; ?></td><td> <?php echo $row['nazev']; ? </td><td>
?php echo $row['ph']; ? </td> <td>
?php
$Number_of_graduates = mysqli_query($cnn, "SELECT COUNT(*) AS abs FROM participant where id_completed_course = $row[id]");
while ($rAbs = mysqli_fetch_array($Number_of_graduates)){
echo $rAbs['abs'];
} ?
</td>
</pre>
The question is. How to convert the second loop where first id from SQL?

Answer 1

Ok, so your question is really about SQL. Let's look at your queries. The first one looks like this:
SELECT *, COUNT(*) AS ph
FROM course
INNER JOIN completed_course ON course.id = completed_course.id_kurz
GROUP BY course.id
I'm assuming (because I don't know anything about your database scheme) that this is going to give a list of courses and the number of students (maybe - I don't know what's in the completed_course table) who completed them. As written, this query is going to also give you some data from the completed_course table, but it's likely to be meaningless since you're grouping only on course.id.
The second query is:
SELECT COUNT(*) AS abs
FROM participant
WHERE id_completed_course = {DATA FROM FIRST QUERY}
Presumably, this query is intended to give you the total number of participants of completed courses. To make that work, the WHERE clause could look like this:
SELECT COUNT(*) AS abs
FROM participant
WHERE id_completed_course IN (
SELECT course.id FROM
FROM course
INNER JOIN completed_course ON course.id = completed_course.id_kurz
)
Notice that I'm taking the values selected in the first query and making them part of an IN clause. This query can be simplified significantly - for instance, the JOIN in the subquery is really only selected ID values from the completed_course table:
SELECT COUNT(*) AS abs
FROM participant
WHERE id_completed_course IN (
SELECT id_kurz
FROM completed_course
)
And the query will actually be more efficient if you get rid of the subquery altogether and just join the participants to the completed_course table.
SELECT COUNT(*) AS abs
FROM participant
INNER JOIN completed_course ON participant.id_completed_course=completed_course.id_kurz
This last query is going to give you one value: the number of participants whose id_completed_course value corresponds to an item in the completed_course table. You can use the mysqli methods to retrieve this data and pass it to your Smarty template.