SQLite Forum

Bug when converting string to boolean?
> To convert the results of an SQL expression to a boolean value, SQLite first casts the result to a NUMERIC value in the same way as a CAST expression. A numeric zero value (integer value 0 or real value 0.0) is considered to be false. A NULL value is still NULL. All other values are considered true.

And the relevant CAST section:

> When casting a TEXT value to INTEGER, the longest possible prefix of the value that can be interpreted as an integer number is extracted from the TEXT value and the remainder ignored. Any leading spaces in the TEXT value when converting from TEXT to INTEGER are ignored. If there is no prefix that can be interpreted as an integer number, the result of the conversion is 0.