Question

I’ve got an Sqlite database where one of the columns is defined as “TEXT NOT NULL”. Some of the values are strings and some can be cast to a DOUBLE and some can be case to INTEGER. Once I’ve narrowed it down to DOUBLE values, I want to do a query that gets a range of data. Suppose my column is named “Value”. Can I do this?

SELECT * FROM Tbl WHERE ... AND Value >= 23 AND Value < 42

Is that going to do some kind of ASCII comparison or a numeric comparison? INTEGER or REAL? Does the BETWEEN operator work the same way?

And what happens if I do this?

SELECT MAX(Value) FROM Tbl WHERE ...

Will it do string or integer or floating-point comparisons?

Answer 1

It is all explained in the Datatypes In SQLite Version 3 article. For example, the answer to the first portion of questions is

An INTEGER or REAL value is less than any TEXT or BLOB value. When an INTEGER or REAL is compared to another INTEGER or REAL, a numerical comparison is performed.

This is why SELECT 9 < '1' and SELECT 9 < '11' both give 1 (true).

The expression “a BETWEEN b AND c” is treated as two separate binary comparisons “a >= b AND a <= c”

The most important point to know is that column type is merely an annotation; SQLite is dynamically typed so each value can have any type.