Which MySQL data type to use for storing boolean values

manpreet Best Answer 2 years ago

Since MySQL doesn't seem to have any 'boolean' data type, which data type do you 'abuse' for storing true/false information in MySQL?

Especially in the context of writing and reading from/to a PHP script.

Over time I have used and seen several approaches:

• tinyint, varchar fields containing the values 0/1,
• varchar fields containing the strings '0'/'1' or 'true'/'false'
• and finally enum Fields containing the two options 'true'/'false'.

None of the above seems optimal. I tend to prefer the tinyint 0/1 variant, since automatic type conversion in PHP gives me boolean values rather simply.

So which data type do you use? Is there a type designed for boolean values which I have overlooked? Do you see any advantages/disadvantages by using one type or another?

manpreet 2 years ago

This is an elegant solution that I quite appreciate because it uses zero data bytes:

some_flag CHAR(0) DEFAULT NULL

To set it to true, set some_flag = '' and to set it to false, set some_flag = NULL.

Then to test for true, check if some_flag IS NOT NULL, and to test for false, check if some_flag IS NULL.

(This method is described in "High Performance MySQL: Optimization, Backups, Replication, and More" by Jon Warren Lentz, Baron Schwartz and Arjen Lentz.)