Pengenalan kueri

Pengantar SQL

Jasmin Ludolf

Senior Data Science Content Developer, DataCamp

Untuk apa SQL berguna?

basis data relasional perpustakaan

Terbaik untuk dataset besar

Tiga pengguna basis data menanyakan pertanyaan bisnis berbeda ke basis data

Kata kunci

Kata kunci adalah kata khusus untuk operasi

SELECT name

SELECT field name

Kata kunci umum: SELECT, FROM sql FROM patrons{ FROM tabel patrons

Kueri pertama kita

SELECT name
FROM patrons;

| name   |
|--------|
| Izzy   |
| Maham  |
| Jasmin |
| James  |

Hasil kueri sering disebut result set

tabel patrons

Memilih beberapa field

SELECT card_num, name
FROM patrons;

| card_num | name   |
|----------|--------|
| 54378    | Izzy   |
| 94722    | Maham  |
| 45783    | Jasmin |
| 90123    | James  |

SELECT name, card_num
FROM patrons;

| name   | card_num |
|--------|----------|
| Izzy   | 54378    |
| Maham  | 94722    |
| Jasmin | 45783    |
| James  | 90123    |

Memilih beberapa field

SELECT name, card_num, total_fine
FROM patrons;

| card_num | name   | total_fine |
|----------|--------|------------|
| 54378    | Izzy   | 9.86       |
| 94722    | Maham  | 0          |
| 45783    | Jasmin | 2.05       |
| 90123    | James  | 0          |

Memilih semua field

SELECT *
FROM patrons;

| card_num | name   | member_year | total_fine |
|----------|--------|-------------|------------|
| 54378    | Izzy   | 2012        | 9.86       |
| 94722    | Maham  | 2020        | 0          |
| 45783    | Jasmin | 2022        | 2.05       |
| 90123    | James  | 1989        | 0          |

Ayo berlatih!

Pengantar SQL