40. Qora ro'yxatda bo'lmagan mijozlar (NULL tuzog'i)
O'rtachaQora ro'yxat blacklist jadvalida saqlanadi, lekin unda client_id ustuni bo'sh
(NULL) bo'lgan yozuvlar ham bor — ma'lumot to'liq kiritilmagan.
Qora ro'yxatga tushmagan mijozlarning client (ismi) ustunini qaytaring.
⚠️ Diqqat: NOT IN bilan yozsangiz natija butunlay bo'sh chiqadi —
NULL bilan taqqoslash UNKNOWN beradi. Boshqa usulni toping.
Saralash: client alifbo.
clients: id INT PK, name VARCHAR
blacklist: id INT PK, client_id INT NULL, reason VARCHAR
Jadval: clients
| Ustun | Turi |
|---|---|
| id | INT PK |
| name | VARCHAR(60) |
Jadval: blacklist
| Ustun | Turi |
|---|---|
| id | INT PK |
| client_id | INT |
| reason | VARCHAR(60) |
Namuna ma'lumotlar
sample-basic
clients
| idINT | nameVARCHAR(60) |
|---|---|
| 1 | Aziz |
| 2 | Bek |
| 3 | Dilnoza |
| 4 | Kamola |
| 5 | Sherzod |
blacklist
| idINT | client_idINT | reasonVARCHAR(60) |
|---|---|---|
| 1 | 2 | Qarzdorlik |
| 2 | 5 | Qarzdorlik |
| 3 | NULL | Aniqlanmagan |
| 4 | NULL | Aniqlanmagan |
Kutilgan natija
| client |
|---|
| Aziz |
| Dilnoza |
| Kamola |
sample-none-blacklisted
clients
| idINT | nameVARCHAR(60) |
|---|---|
| 1 | Aziz |
| 2 | Bek |
| 3 | Dilnoza |
Kutilgan natija
| client |
|---|
| Aziz |
| Bek |
| Dilnoza |
sample-only-nulls
clients
| idINT | nameVARCHAR(60) |
|---|---|
| 1 | Aziz |
| 2 | Bek |
| 3 | Dilnoza |
blacklist
| idINT | client_idINT | reasonVARCHAR(60) |
|---|---|---|
| 1 | NULL | Aniqlanmagan |
| 2 | NULL | Aniqlanmagan |
Kutilgan natija
| client |
|---|
| Aziz |
| Bek |
| Dilnoza |
O'xshash masalalar
Konsol
Natijani ko'rish uchun so'rovni ishga tushiring.