In 2.4 of the [SELECT](https://www.sqlite.org/lang_select.html) documentation there's this: > 4 . Removal of duplicate rows (DISTINCT processing). > One of the ALL or DISTINCT keywords may follow the SELECT keyword in a simple SELECT statement. If the simple SELECT is a SELECT ALL, then the entire set of result rows are returned by the SELECT. If neither ALL or DISTINCT are present, then the behavior is as if ALL were specified. If the simple SELECT is a SELECT DISTINCT, then duplicate rows are removed from the set of result rows before it is returned. For the purposes of detecting duplicate rows, two NULL values are considered to be equal. The usual rules apply for selecting a collation sequence to compare text values. So it looks like it uses =/IS to compare them. And since 1 = 1.0 they're considered the same. Which one you get back is probably which one came first as it was traversing the values.