For character and string columns, follow these guidelines:
Use binary collation order for fast comparison and sort operations, when you do not need language-specific collation features. You can use the BINARY operator to use binary collation within a particular query.
When comparing values from different columns, declare those columns with the same character set and collation wherever possible, to avoid string conversions while running the query.
For column values less than 8KB in size, use binary
VARCHAR instead of
ORDER BY clauses can generate
temporary tables, and these temporary tables can use the
MEMORY storage engine if the original
table does not contain any
If a table contains string columns such as name and address, but many queries do not retrieve those columns, consider splitting the string columns into a separate table and using join queries with a foreign key when necessary. When MySQL retrieves any value from a row, it reads a data block containing all the columns of that row (and possibly other adjacent rows). Keeping each row small, with only the most frequently used columns, allows more rows to fit in each data block. Such compact tables reduce disk I/O and memory usage for common queries.
When you use a randomly generated value as a primary key
InnoDB table, prefix it with an
ascending value such as the current date and time if
possible. When consecutive primary values are physically
stored near each other,
insert and retrieve them faster.
See Section 126.96.36.199, “Optimizing for Numeric Data” for reasons why a numeric column is usually preferable to an equivalent string column.