How to select rows from two tables using MySQL? - mysql

Question

I want to select information from two SQL tables within one query.
table1
id | postID | status | number | userID | active
1 | 1 | 100 | 100 | 3 | 1
2 | 7 | 50 | 25 | 5 | 1
3 | 3 | 75 | 50 | 3 | 1
table2
postID | reference | joint_date | userID | remove
1 | 100 | 100 | 3 | 1
2 | 50 | 25 | 5 | 1
3 | 50 | 50 | 3 | 0
Expected Output
postID | status | number | reference | joint_date
1 | 100 | 100 | 100 | 100
3 | 75 | 50 | 50 | 50
This is my try:
$userID = 12;
$active = 1;
$remove= 1;
$sql = "SELECT table1.status, table1.number, table2.reference, table2.joint_date
FROM table1
WHERE table1.active=:active AND table1.userID=:userID
INNER JOIN table2 ON table1.postID=table2.postID
WHERE table2.postID=:userID
AND table2.remove=:remove
ORDER BY table1.postID DESC";
$stmt = $this->pdo->prepare($sql);
$stmt->bindValue(":active", $active, PDO::PARAM_INT);
$stmt->bindValue(":userID", $userID, PDO::PARAM_INT);
$stmt->bindValue(":remove", $remove, PDO::PARAM_INT);
$stmt->execute();
What is wrong with my query?

Answer 1

What is wrong with my query?
The clauses/statements order are wrong
SELECT....FROM....WHERE....AND....AND....ORDER BY..
You can not have two WHERE condition in the same SELECT (do not take in consideration subqueries)
There is no way you can get the expected result based on the given static variables
Based on the data example you have two condition which will never be true at the same time.
AND t2.postID=3 --- > t2.remove is equal to 0 then you specify
AND t2.remove=1
You can use below example to properly filter based on your conditions:
SELECT t1.postID,
t1.status,
t1.`number`,
t2.reference,
t2.joint_date
FROM table1 t1
INNER JOIN table2 t2 ON t1.postID=t2.postID
WHERE t1.active=1
AND t1.userID=3
ORDER BY t1.postID ASC;
Result:
postID status number reference joint_date
1 100 100 100 100
3 75 50 50 50
Note. I removed both conditions table2.postID=:userID AND table2.remove=:remove
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=78b0f07c7d1dd1db1008e415fc005e85