MySQL String Types: VARCHAR vs TEXT vs CHAR

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TL;DR

Explanation

CHAR(n) pads shorter values with spaces — slightly faster for fixed-length data. VARCHAR(n) stores actual length + 1-2 bytes overhead. TEXT (64KB), MEDIUMTEXT (16MB), LONGTEXT (4GB) store large content off the main row page — cannot be fully indexed without a prefix length and cannot have DEFAULT values. VARCHAR up to 767 bytes (InnoDB row format default) supports full-column indexing. For utf8mb4, the index limit is 191 characters on older InnoDB row formats.

Common Misconception

Why It Matters

Common Mistakes

• Using TEXT for email, name, or slug columns — no DEFAULT, no full-column index.
• Using CHAR(255) for variable-length data — pads every row regardless of actual content length.
• Forgetting that utf8mb4 VARCHAR(255) requires 255×4=1020 bytes — exceeds the 767-byte InnoDB index limit on older row formats.

Avoid When

• Avoid TEXT for columns that need DEFAULT values or full-column unique indexes.
• Avoid CHAR for variable-length content — every row is padded to the declared length.

When To Use

• Use VARCHAR(255) as the default for most string columns — fully indexable and flexible.
• Use TEXT/MEDIUMTEXT/LONGTEXT for article bodies, descriptions, or any content over 1KB.
• Use CHAR for truly fixed-length values: country codes (CHAR(2)), currency codes (CHAR(3)), UUIDs (CHAR(36)).

Code Examples

-- TEXT for short fields: no DEFAULT, no full index
email TEXT NOT NULL,
-- CHAR(100) wastes 100 bytes even for 'Bob'
name CHAR(100) NOT NULL

CREATE TABLE users (
    id           INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    email        VARCHAR(255) NOT NULL UNIQUE,
    country_code CHAR(2)      NOT NULL DEFAULT 'GB',
    bio          TEXT,
    slug         VARCHAR(100) NOT NULL UNIQUE
) ENGINE=InnoDB CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC;

References

• ↗ https://dev.mysql.com/doc/refman/8.0/en/string-types.html

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