CODEWITHSUNDEEP
mysqlindexingquery-optimization
YD8877
YD8877

Reputation: 10780

what happens if we define column lengths as more than required?

I had a friend tell me that never to declare varchar as (255) if we will be only using 20 characters. Same for an INT.

Performance wise, Is this true ? Can i achieve a performance gain by reducing the size of my columns ? What exactly happens when i declare a column as 255 ?

Upvotes: 1

Views: 74

Answers (2)

Dre
Dre

Reputation: 4329

Using TINYINT instead of INT if you only need the size of a TINYINT will save a few bytes per row.

A VARCHAR(255) will not use more then a VARCHAR(20) if you always only use 20 characters ( CHAR(255) on the other hand might use more then CHAR(20) )

Upvotes: 1

The Scrum Meister
The Scrum Meister

Reputation: 30111

In most cases there will be no performance gain with shorter VARCHAR columns.

1 of the cases where there will be a performance gains, If you have a MEMORY table - a in memory temp table, MySql will allocate memory for the length of the column.

From the docs:

MEMORY tables use a fixed-length row-storage format. Variable-length types such as VARCHAR are stored using a fixed length.

Upvotes: 2

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