Introduction

The "only one TIMESTAMP column" rule is mostly an old MySQL quirk, not a universal SQL principle. In older MySQL versions, automatic timestamp initialization and update logic was hardwired in a restrictive way, so only one TIMESTAMP column could use the special current-time behavior comfortably.

Understand the Historical MySQL Behavior

Older MySQL releases treated TIMESTAMP as a special auto-managed type rather than just another datetime column. The engine gave one TIMESTAMP column privileged behavior for automatic initialization or automatic update handling, which is why developers ran into errors when trying to define several timestamp columns with current-time defaults.

An example of the kind of table that caused trouble on older servers is:

1CREATE TABLE audit_demo (
2    id INT PRIMARY KEY,
3    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
4    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
5);

On a modern server, this is normal. On an older one, the automatic behavior around TIMESTAMP could be restricted enough to reject or awkwardly reinterpret a design like this.

Why the Restriction Existed

The short explanation is implementation history. Early MySQL versions bundled special rules into TIMESTAMP handling rather than treating each column definition independently. Supporting multiple auto-initialized or auto-updated timestamp columns would have required a more flexible implementation and more nuanced compatibility rules.

So the restriction existed because:

• 'TIMESTAMP had built-in engine magic'
• The implementation was intentionally narrow
• Backward compatibility preserved that behavior for years

That is very different from saying databases in general cannot support several timestamp columns with current-time defaults. They can. The limitation was mostly about old MySQL behavior.

Distinguish DEFAULT CURRENT_TIMESTAMP from ON UPDATE CURRENT_TIMESTAMP

Two features are often blurred together:

• 'DEFAULT CURRENT_TIMESTAMP'
• 'ON UPDATE CURRENT_TIMESTAMP'

The first sets an initial value during insert. The second refreshes the column when the row is updated. In historical MySQL behavior, the interaction between these features and multiple TIMESTAMP columns was the real source of confusion.

It helps to think in terms of audit semantics rather than syntax. A created_at column usually wants only the default-on-insert rule. An updated_at column typically wants the auto-update rule as well. A reviewed_at column may want neither and should instead be set explicitly by application logic.

Modern MySQL Is More Flexible

Newer MySQL releases, especially from MySQL 5.6.5 onward, relaxed the old restriction significantly. Multiple TIMESTAMP and DATETIME columns can use current-time defaults and update clauses in ways that older servers did not allow.

For example, this is a reasonable modern schema:

1CREATE TABLE audit_demo (
2    id INT PRIMARY KEY,
3    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
4    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
5    reviewed_at DATETIME DEFAULT CURRENT_TIMESTAMP
6);

If you still hit the old limitation today, the first thing to check is server version and compatibility settings rather than assuming the schema design itself is impossible.

Common Pitfalls

The most common mistake is treating the old MySQL rule as a general SQL law. It was not.

Another issue is confusing the insert-time default with the update-time clause. They solve different problems, and mixing them up makes timestamp design harder than it needs to be.

People also sometimes rely on automatic timestamp behavior without being clear about the business meaning of each column. Just because a column can default to the current time does not mean it should.

Summary

• The one-column restriction was mainly a historical MySQL behavior, not a universal SQL rule.
• Old MySQL versions gave TIMESTAMP special auto-managed behavior that was intentionally limited.
• 'DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP solve different audit problems.'
• Modern MySQL versions are much more flexible about multiple timestamp columns.
• When designing audit columns, start with the semantics you want and then choose the database features that match them.