Apa fungsi string lan date sing umum?

Question

Accepted Answer

SQL nyediyakake fungsi built-in kanggo manipulasi **strings** lan **dates** — formatting, ngenei bagian, ngetung bedane. Iki penting kanggo transformasi data lan query berbasis tanggal, sanajan jeneng sing tepat beda-beda nang dialek database.

## Fungsi string sing umum

```sql
SELECT
  UPPER(name), LOWER(name),               -- case conversion
  LENGTH(name),                           -- string length
  CONCAT(first_name, ' ', last_name),      -- join strings (or || in some DBs)
  SUBSTRING(name, 1, 3),                   -- extract a substring
  TRIM(name),                              -- remove surrounding whitespace
  REPLACE(phone, '-', ''),                 -- replace text
  LEFT(name, 3), RIGHT(name, 3),           -- leftmost/rightmost chars
  POSITION('@' IN email)                   -- find a substring's position
FROM users;
```

Fungsi string ngubah lan ngowohi teks — guna kanggo formatting output, cleaning data, lan building computed values.

## Fungsi date/time sing umum

```sql
SELECT
  NOW(), CURRENT_DATE, CURRENT_TIMESTAMP,   -- current date/time
  EXTRACT(YEAR FROM created_at),            -- get a part (YEAR, MONTH, DAY, HOUR...)
  DATE_TRUNC('month', created_at),          -- truncate to a unit (Postgres)
  created_at + INTERVAL '7 days',           -- date arithmetic (add time)
  AGE(NOW(), birth_date),                   -- difference between dates (Postgres)
  TO_CHAR(created_at, 'YYYY-MM-DD')         -- format a date as text (Postgres)
FROM events;
```

Fungsi date ngetok wektu saiki, ngowohi bagian (taun, bulan), ngerjakake aritmetika (add/subtract intervals), ngetung bedane, lan formatting tanggal — penting kanggo query berbasis wektu lan reporting.

## Pola umum: grouping nang periode wektu

```sql
-- count events per month (a frequent reporting need)
SELECT
  DATE_TRUNC('month', created_at) AS month,
  COUNT(*) AS event_count
FROM events
GROUP BY DATE_TRUNC('month', created_at)
ORDER BY month;
```

Grouping nang bagian tanggal sing wis diwowohi/ditruncate (bulan, dinten, taun) iku pola reporting sing umum banget.

## Perbedaan dialek (caveat penting)

```text
⚠️ Function names/syntax VARY significantly by database:
  String concat: CONCAT() vs || vs +
  Date functions: DATE_TRUNC/EXTRACT (Postgres) vs DATE_FORMAT (MySQL) vs DATEPART (SQL Server)
→ Check YOUR database's documentation; the concepts transfer, the exact syntax differs.
```

## Kok iki penting

Fungsi string lan date iku alat SQL sing penting lan praktis — manipulasi teks lan kerja karo tanggal iku requirement sing konstan ing query nyata (formatting output, cleaning data, filtering lan reporting berbasis wektu), dadi ngerti-ngertenono iku ilmu sing berharga saben hari. **Fungsi string** (case conversion, concatenation, substring, replace, trim) nangani transformasi teks lan cleaning, sing ana ing akeh query kanggo formatting lan data manipulation. **Fungsi date** iku luwih penting amarga **query lan reporting berbasis wektu iku mbenake** — ngetok wektu saiki, ngowohi bagian tanggal (taun, bulan), aritmetika tanggal (nambah intervals, ngetung bedane), lan formatting tanggal iku butuh kanggo filtering nang date ranges, ngetung umur/durasi, lan luwih-luwih **grouping nang periode wektu** (counts per bulan/dinten — pola reporting sing umum banget).

Ngerti fungsi-fungsi iki ngidini iku nangani manipulasi teks lan tanggal sing aplikasi nyata butuh terus-terusan.

Caveat praktis penting iku **jeneng fungsi lan syntax beda-beda banget nang dialek database** (concatenation string lan fungsi date beda banget antara PostgreSQL, MySQL, SQL Server) — dadi ngerti konsep-konsepne (sing transfer) nalika cek syntax database mu sing spesifik iku penting.

Amarga manipulasi string lan tanggal iku butuh sering-sering nang querying, reporting, lan data processing, lan amarga filtering lan grouping berbasis tanggal iku pusat analytics, ngerti fungsi string lan date sing umum — lan krasan karo perbedaan dialek — iku ilmu SQL sing guna, sering-sering dipenggo, lan penting kanggo kerja data sing praktis.