table_design_faq

Troubleshooting Table Design

This topic provides answers to some frequently asked questions about table design.

What is the maximum length of the VARCHAR type and how does the length affects query performance?

The maximum length of the VARCHAR type is 65533, which requires 1 MB storage size. It is recommended to set the VARCHAR length to a minimum value that is necessary. It is because, despite that the VARCHAR type data size is based on the actual length, in query scenarios where memory pre-allocation is required, memory resources are allocated based on the pre-defined length of the VARCHAR types instead of the actual length. For example, for an address field, 100 bytes is enough, which means that VARCHAR(100) is recommended over STRING, because the STRING type is equivalent to VARCHAR(65533).