Get value from table with 3 unique ID's (redundant sql query) - php

Question

$query = "SELECT COUNT(id) FROM complaint WHERE ID_complntCategory = ?";
$complntCategory = $database->prepare($query);
try {
$complntCategory->execute(array());
$complntCategory->setFetchMode(PDO::FETCH_ASSOC);
foreach ($complntCategory as $key) {
$totaalM = $key['1'];
$totaalV = $key['2'];
$totaalG = $key['3'];
}
}
catch(PDOException $e) {
echo "Error";
}
Above you see my PHP code, and here is what I'm trying to do:
I'm trying to get the amount of rows from the table 'complaint' into 3 different variables (totaalM, totaalV and totaalG). The totaalM variable should contain the amount of rows 'WHERE ID_complntCategory = 1'.
For the other variables the 'ID_complntCategory' should be 2 and 3
('ID_complntCategory' is either 1, 2 or 3)
There should be a way where I don't have to write 3 queries, right?
I'm clearly approaching this the wrong way, and I'm not sure how I should tackle this problem...

Answer 1

What you are trying to do is called pivot rows into columns, but MySQL doesn't have pivot table operator like other RDBMS, but you cane use the case expression like this in one query:
SELECT
SUM(CASE WHEN ID_complntCategory = 1 THEN 1 ELSE 0 END) AS totaalM,
SUM(CASE WHEN ID_complntCategory = 2 THEN 1 ELSE 0 END) AS totaalV,
SUM(CASE WHEN ID_complntCategory = 3 THEN 1 ELSE 0 END) AS totaalG,
COUNT(Id) AS Total
FROM complaint;
Or you can make it shorter like this:
SELECT
SUM(ID_complntCategory = 1) AS totaalM,
SUM(ID_complntCategory = 2) AS totaalV,
SUM(ID_complntCategory = 3) AS totaalG,
COUNT(Id) AS Total
FROM complaint;
Demo
This will give you something like this:
| totaalM | totaalV | totaalG | Total |
|---------|---------|---------|-------|
| 2 | 3 | 1 | 7 |

Answer 2

Here you need some magic, involving special SQL and PDO features.
First, you need an SQL query that is giving you desired results in one query. To get that you need a GROUP BY operator:
SELECT ID_complntCategory, count(*) FROM complaint GROUP BY ID_complntCategory
it will give you counts split by ID_complntCategory.
Next, you can use one of PDO's magnificent features, PDO::FETCH_KEY_PAIR fetch mode, that will give you an array where key would be category id and value is count
$sql = "SELECT ID_complntCategory, count(*) FROM complaint GROUP BY ID_complntCategory";
$stmt = $database->prepare($sql);
$key = $stmt->fetchAll(PDO::FETCH_KEY_PAIR);
$totaalM = $key['1'];
$totaalV = $key['2'];
$totaalG = $key['3'];
note that you should never catch a PDO errors only to say "error". Let PHP error reporting to do it instead.