Sunday, November 7, 2010

Select Odd Rows in MySQL

Any time you can use a bitwise operator in place of a function call, it's a good thing. Selecting odd rows from a table in MySQL that have an auto_increment primary key is no exception.

SELECT * FROM mytable WHERE id & 1;

If you're unfamiliar with a bitwise AND, basically what it says is return true of the left operand has the same bits set as the right operand. The number 1 only has one bit set, and conveniently enough that one bit is the same bit that will only be present in odd numbers.


Anonymous said...

What about even?

Stanislav said...

And what about a situation when you have deleted some rows and have id=2, id=4 etc.?