What is the True Maximum Size of a MySQL VARCHAR Column, and How is it Affected by Row Size and Character Sets?

The Intriguing Enigma of MySQL VARCHAR Max Size

Introduction:
The VARCHAR data type in MySQL offers flexibility in storing variable-length strings, but its limits can be a mystery to database enthusiasts. This article unravels the elusive nature of the MySQL VARCHAR max size and delves into the factors that govern its boundaries.

The Row Size Conundrum:
Contrary to popular belief, the maximum size of a VARCHAR column is not directly determined by the row size limit of approximately 65k. This limit applies to the entire row, including all column values, not just VARCHAR fields.

Evolution of VARCHAR Max Size:
Prior to MySQL version 5.0.3, VARCHAR columns could only accommodate strings up to a maximum length of 255 characters. However, with the advent of 5.0.3 and later versions, this limit was dramatically increased to a staggering 65,535 characters.

Character Set Considerations:
While the fundamental max size for VARCHAR is 65,535 characters, the choice of character set can further constrain this limit. Multi-byte character sets like UTF-8 or UTF-8mb4 require more storage space, effectively reducing the maximum length of VARCHAR strings.

Overcoming Row Size Limits with TEXT Types:
For scenarios that demand storing extremely large strings, MySQL offers the TEXT data types. These types, including TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT, are designed to handle vast amounts of text and sidestep the row size limitation.

Additional Resources for Insight:

• MySQL Data Type Storage Requirements: https://dev.mysql.com/doc/refman/8.0/en/data-types.html#data-type-storage-requirements

• MySQL VARCHAR Reference:

  • MySQL v8.0: https://dev.mysql.com/doc/refman/8.0/en/varchar.html
  • MySQL v5.7: https://dev.mysql.com/doc/refman/5.7/en/varchar.html
  • MySQL v5.6: https://dev.mysql.com/doc/refman/5.6/en/varchar.html

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