Fungsi agregat ngitung siji nilai saka set baris — COUNT, SUM, AVG, MIN, MAX. Iku penting banget kanggo merangkum data (total, rata-rata, jumlah), utamane digabung karo .
Fungsi agregat ngitung siji nilai saka set baris — COUNT, SUM, AVG, MIN, MAX. Iku penting banget kanggo merangkum data (total, rata-rata, jumlah), utamane digabung karo .
GROUP BYSELECT
COUNT(*) AS total_rows, -- count all rows
COUNT(email) AS rows_with_email, -- count NON-NULL emails (ignores NULLs!)
SUM(amount) AS total_amount, -- sum of a column
AVG(price) AS average_price, -- average
MIN(price) AS lowest, -- minimum
MAX(price) AS highest -- maximum
FROM orders;
Saben fungsi nyuda akeh baris dadi siji nilai. SUM/AVG kerja ing angka; MIN/MAX ing angka, tanggal, utawa teks; COUNT ing apa wae.
COUNT(*) -- counts ALL rows (including those with NULLs)
COUNT(email) -- counts only rows where email is NOT NULL
COUNT(DISTINCT country) -- counts UNIQUE non-null values
COUNT(*) ngetung kabeh baris, nanging COUNT(column) ngetung mung baris sing kolom kasebut ora NULL — perbedaan sing halus nanging penting. COUNT(DISTINCT col) ngetung nilai unik.
-- aggregate PER GROUP instead of the whole table
SELECT country, COUNT(*) AS users, AVG(age) AS avg_age
FROM users
GROUP BY country; -- one result row per country
-- → for each country: how many users and their average age
Tanpa GROUP BY, agregat merangkum kabeh hasil dadi siji baris. Karo GROUP BY, iku ngasilke siji baris ringkasan per grup — cara sing tipikal lan kuwat.
-- ❌ ERROR — can't mix an aggregate with a non-grouped column
SELECT name, COUNT(*) FROM users; -- which name? ambiguous
-- ✅ either group by it, or only select aggregates
SELECT country, COUNT(*) FROM users GROUP BY country;
Fungsi agregat kuwat banget kanggo merangkum lan menganalisis data — ngitung total, rata-rata, jumlah, lan ekstrem iku butuh terus ing laporan, analitik, dashboard, lan logika aplikasi, mula mangerti iku katrangan SQL dasar.
Mangerti fungsi utama (COUNT, SUM, AVG, MIN, MAX) lan carane nyuda set baris dadi nilai tunggal iku perlu kanggo ringkasan data apa wae.
Detail penting sing sering disalengo yaiku perbedaan COUNT(*) lawan COUNT(column) (COUNT(*) ngetung kabeh baris, COUNT(column) ngetung mung nilai non-NULL — sing bisa ngasilake asil beda lan ngejutake), balung karo COUNT(DISTINCT) kanggo nilai unik.
Paling kuwat, agregat gabung karo GROUP BY kanggo ngasilake ringkasan per-grup (jumlah/rata-rata per kategori) — fondasi saka pitakonan analitik.
Mangerti pitakonan yen ora bisa campur agregat karo kolom sing ora digabung (kesalahan umum) uga penting.
Amerga merangkum data iku tugas database sing serba-serbi (laporan, dashboard, lan pitakonan analitik apa wae nggunake agregat), lan mangerti fungsi, nuansa COUNT, lan utamane gabungan karo GROUP BY iku dasar kanggo analisis data ing SQL, nguasai fungsi agregat iku katrangan inti sing sering diterapake penting kanggo kerja karo data — mbridging pitakonan dasar lan kekuwatan analitik ringkasan sing nggawe SQL berharga kanggo laporan lan wawasan.