SQL data types define the kind of data a column can store. They ensure:
🔒 Data integrity
⚙️ Efficient storage
🧠 Correct query processing
🧮 Numeric Data Types
🔢 INT, SMALLINT, BIGINT – For whole numbers
🔣 DECIMAL(p, s), NUMERIC(p, s) – For precise decimal values (used in money, percentages)
💧 FLOAT, REAL, DOUBLE – For approximate decimal numbers (can lose precision)
📄 Character/String Data Types
Variable-Length Types
🧶 VARCHAR(n) – Stores up to n characters
🧰 Allocates only the space needed for actual data
💡 Efficient for values of varying lengths
📌 Example:
name VARCHAR(50)Stores "Swastika" using just 8 characters, not the full 50
Fixed-Length Types
🧰 CHAR(n) – Always uses exactly n characters
🧱 Pads with spaces if the value is shorter
📌 Example:
code CHAR(4)Stores "AB" as "AB " (with 2 spaces)
⚔️ Variable vs Fixed: Key Differences
Feature |
|
|
|---|---|---|
Length Usage | Stores only used characters | Always uses full length |
Storage | Space-efficient | May waste space |
Performance | Slightly slower on updates | Faster for fixed-length |
Use Case | Names, emails, descriptions | PINs, codes, fixed-size IDs |
📅 Date and Time Data Types
📆 DATE – Stores date (YYYY-MM-DD)
⏰ TIME – Stores time (HH:MM:SS)
🕒 DATETIME – Stores both date and time
🕯️ TIMESTAMP – Auto-updated with current date & time (useful for logs)
🧱 Other Data Types
📦 BLOB – Binary Large Object (images, files)
📑 TEXT – Long-form text
🟢 BOOLEAN – Stores TRUE / FALSE (some databases use TINYINT)
✅ Summary
🧵 Use VARCHAR for fields with variable lengths (e.g., names, emails)
📐 Use CHAR for fields with fixed lengths (e.g., country codes, OTPs)
💾 Choosing the right type improves performance, storage efficiency, and data accuracy