SQL.What is the difference between CHAR, VARCHAR, and TEXT, and when would you choose each?

Short answer (what to say first)

CHAR is fixed-length and space-padded, VARCHAR is variable-length with a limit, and TEXT is variable-length without a defined limit.
In practice, VARCHAR is the default choice, CHAR is for truly fixed-size values, and TEXT is for large or unbounded content.

1️⃣ CHAR(n)

What it is

• Fixed-length string
• Always uses n characters
• Right-padded with spaces

CHAR(10)

Example

'abc' → 'abc       '

When to use

• Truly fixed-size data:
  • ISO country codes (CHAR(2))
  • Fixed flags
  • Legacy schemas

Pros / Cons

✅ Predictable size
❌ Wastes space
❌ Easy to misuse

Interview note

CHAR rarely improves performance in modern DBs.

2️⃣ VARCHAR(n)

What it is

• Variable-length string
• Enforced maximum length
• No padding

VARCHAR(255)

Example

'abc' → 'abc'

When to use (most cases)

• Names
• Emails
• Codes with max length
• API input validation at DB level

Pros / Cons

✅ No wasted space
✅ Length constraint protects data
❌ Slight length overhead (negligible)

Interview note

Default choice for application data.

3️⃣ TEXT

What it is

• Variable-length
• No declared limit (technically very large)
• Stored like other varlena types in Postgres

TEXT

When to use

• Long descriptions
• JSON blobs (sometimes)
• Logs
• Comments / messages

Pros / Cons

✅ No artificial limit
❌ Harder to reason about size
❌ Sometimes discouraged in strict schemas

Interview note

TEXT and VARCHAR have similar performance in PostgreSQL.

Type	Fixed	Max length	Padding	Typical use
CHAR(n)	✅	Yes	Yes	Country codes, legacy
VARCHAR(n)	❌	Yes	No	Most app fields
TEXT	❌	No	No	Large free text

5️⃣ Performance & indexing (important)

• Postgres treats TEXT and VARCHAR almost identically
• Index performance is the same
• Length limit is a semantic constraint, not a performance one

Bad myth:

“VARCHAR(255) is faster than TEXT”

❌ False in Postgres.

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6️⃣ When NOT to use each

❌ Don’t use CHAR(n) for names or emails
❌ Don’t use TEXT when business rules require a max length
❌ Don’t pick VARCHAR(255) blindly “because everyone does”

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7️⃣ Interview-ready final answer (2–3 sentences)

“CHAR is fixed-length and space-padded, suitable only for truly fixed-size values.
VARCHAR is variable-length with a maximum and is the default choice for most application fields.
TEXT has no declared limit and is used for large or unbounded content; in PostgreSQL it performs similarly to VARCHAR.”

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Senior bonus insight ⭐

In well-designed schemas:

• Length limits express business constraints
• Not performance tuning