Jifunze tofauti kati ya MySQL IS NULL na = NULL, common mistakes zinazotokea kwenye PHP MySQL, na jinsi ya kutumia queries sahihi bila errors.

Utangulizi

Wakati unaandika PHP MySQL queries, moja ya changamoto zinazokutana developers wengi ni kutumia NULL values. Kutokuelewa tofauti kati ya:

IS NULL

= NULL

inaweza kusababisha matokeo yasiyotarajiwa au query failures.

Katika post hii, tutajifunza tofauti, makosa ya kawaida, na fixes.

Tofauti Kuu Kati ya IS NULL na = NULL
1️⃣ IS NULL

Inatumiwa kuangalia kama column ina NULL value

SELECT * FROM students WHERE date_paid IS NULL;

✔ Sahihi kwa queries zinazohitaji kuangalia NULL

2️⃣ = NULL

Hii haifanyi kazi kama unavyotarajia

SQL haikubali comparison ya kawaida na NULL

❌ Wrong:

SELECT * FROM students WHERE date_paid = NULL;

Result = 0 rows, hata kama kuna NULLs

Common Mistakes Developers Wanafanya

Kutumia = badala ya IS NULL

Kutumia <> NULL badala ya IS NOT NULL

Kusahau ku-check input kutoka PHP kabla ya query

Kuangalia string 'NULL' badala ya SQL NULL

Fix Sahihi (MySQLi)
$sql = "SELECT * FROM students WHERE date_paid IS NULL";
$result = mysqli_query($conn, $sql);


while($row = mysqli_fetch_assoc($result)){
echo $row['name'] . '<br>';
}
Fix Sahihi (PDO)
$stmt = $pdo->prepare("SELECT * FROM students WHERE date_paid IS NULL");
$stmt->execute();
$data = $stmt->fetchAll();


foreach($data as $row){
echo $row['name'] . '<br>';
}
Debug Tips

✔ Kumbuka IS NULL vs = NULL

✔ Validate PHP variables kabla ya query

✔ Angalia database schema (column types)

✔ Use IS NOT NULL kwa rows ambazo si NULL