Hot to use custom SQL functions in the WHERE clause - sqlite

Question

I'm trying to make a where clause with custom functions applied to the columns using Knex.js.
Suppose I have a table named tableName with columns named col1, col2, col3 and a function f that receives as parameter something that is the same type of the things that are in col1 and col2.
I also have two variables named var1 and var2 (defined beforehand) that are the same type of the thing returned by f. I tried some ways.
Example 1:
let rows = knexClient("tableName").whereRaw('f(?) <= ${var1} AND f(?) >= ${var2}', [col1, col2]).then((rows) => {
for (row of rows) {
console.log('${row["col1"]} ${row["col2"]} ${row["col3"]}');
}
}).catch((err) => {
console.log(err);
throw err;
});
This gives the following error:
ReferenceError: col1 is not defined.
Example 2:
let rows = knexClient("tableName").whereRaw("f(col1) <= ? AND f(col2) >= ?", [var1, var2]).then((rows) => {
for (row of rows) {
console.log('${row["col1"]} ${row["col2"]} ${row["col3"]}');
}
}).catch((err) => {
console.log(err);
throw err;
});
This gives the following error:
SQLITE_ERROR: no such column: col1] {
errno: 1,
code: 'SQLITE_ERROR'
}
What is the right way to do it? I have searched around and saw some people doing things similar to my first try here. But it didn't work for me.

Answer 1

You can't bind column names dynamically (i.e. using ? placeholders), that only works for values.
The following:
var var1 = 10, var2 = 20;
knex("tableName")
.whereRaw("f(col1) <= ?", var1)
.whereRaw("f(col2) => ?", var2)
.select();
results in generated SQL like this:
select
*
from
tableName
where
f(col1) <= 10
and f(col2) => 20
If you have variables that contain the target column names, you need to format them in yourself:
var col1 = "some_col", col2 = "other_col";
var var1 = 10, var2 = 20;
knex("tableName")
.whereRaw(`f(${col1}) <= ?`, var1)
.whereRaw(`f(${col2}) => ?`, var2)
.select();
which produces
select
*
from
tableName
where
f(some_col) <= 10
and f(other_col) => 20