Flags in a database rows, best practices

Question

I am asking this out of a curiosity. Basically my question is when you have a database which needs a row entry to have things which act like flags, what is the best practice

Answer 1

For many cases, it depends on a lot of things - like your database backend. If you're using MySQL, for example, the SET datatype is exactly what you want.

Basically, it's just a bitmask, with values assigned to each bit. MySQL supports up to 64-bit values (meaning 64 different toggles). If you only need 8, then it only takes a byte per row, which is pretty awesome savings.

If you honestly have more than 64 values in a single field, your field might be getting more complicated. You may want to expand then to the BLOB datatype, which is just a raw set of bits that MySQL has no inherent understanding of. Using this, you can create an arbitrary number of bit fields that MySQL is happy to treat as binary, hex, or decimal values, however you need. If you need more than 64 options, create as many fields as is appropriate for your application. The downside is that is is difficult to make the field human readable. The BIT datatype is also limited to 64.