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7.1.1 MySQL Design Limitations and Tradeoffs
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When using the `MyISAM' storage engine, MySQL uses extremely fast table
locking that allows multiple readers or a single writer. The biggest
problem with this storage engine occurs when you have a steady stream
of mixed updates and slow selects on a single table. If this is a
problem for certain tables, you can use another storage engine for
them. See storage-engines.
MySQL can work with both transactional and non-transactional tables. To
make it easier to work smoothly with non-transactional tables (which
cannot roll back if something goes wrong), MySQL has the following
rules. Note that these rules apply _only_ when not running in strict
SQL mode or if you use the `IGNORE' specifier for `INSERT' or `UPDATE'.
* All columns have default values.
* If you insert an inappropriate or out-of-range value into a
column, MySQL sets the column to the `best possible value' instead
of reporting an error. For numerical values, this is 0, the
smallest possible value or the largest possible value. For
strings, this is either the empty string or as much of the string
as can be stored in the column.
* All calculated expressions return a value that can be used instead
of signaling an error condition. For example, 1/0 returns `NULL'.
To change the preceding behaviors, you can enable stricter data
handling by setting the server SQL mode appropriately. For more
information about data handling, see constraints,
server-sql-mode, and insert.
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