Search code examples
mysqlsqlsqldatatypes

How many bytes does an unsigned DECIMAL(3,2) use in MySQL

I was wondering how many bytes an unsigned DECIMAL(3,2) uses in SQL. The documentation that I find online is not very clear, especially not when you have an unsigned DECIMAL.

Solution

  • The documentation seems pretty clear:

    Values for DECIMAL columns are stored using a binary format that packs nine decimal digits into 4 bytes. The storage requirements for the integer and fractional parts of each value are determined separately. Each multiple of nine digits requires 4 bytes, and any remaining digits left over require some fraction of 4 bytes. The storage required for remaining digits is given by the following table.

    So, the integer part of DECIMAL(3, 2) has 1 digit and the fractional part has 2 digits. According to the table, 1-2 digits require one byte. Hence the total is two bytes.