Known errors and design deficiencies in MySQL

• You can not build in another directory when using mit-pthreads. Since this requires changes to mit-pthreads we are not likely to fix this.
• HAVING can only use fields in select expression list. Functions must be aliased.
• Blobs can't 'reliably' be used in GROUP BY or ORDER BY or DISTINCT. Only the first max_sort_length (default 1024) are used when comparing blobs in these cases. This can be changed with the -O max_sort_length parameter to mysql. A workaround for most cases is to use a substring: SELECT DISTINCT LEFT(blob,2048) FROM table.
• Calculation is done with bigint or double (both are normally 64 bit long). It depends on the function which precision one gets. The general rule is that bit functions are done with bigint precision, IF, and ELT() with bigint or double precision and the rest with double precision.
• All field types are fixed point fields. That means one must specify how many decimals a floating point field shall have. All results will be returned with the correct number of decimals.
• All string columns, except BLOBS, have automatically all end spaces removed when retrieved. For CHAR types this is ok may be regarded as a feature according to ANSI SQL92. The bug is that VARCHAR columns are treated the same way. And a compare with a string constat should remove spaces too. For example the following query never returns anything if name isn't a BLOB. SELECT * FROM table WHERE name = 'david '

For platform specific bugs see the sections about compiling and porting.

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