websql use select in to get rows from an array - sql

Question

in websql we can request a certain row like this:
tx.executeSql('SELECT * FROM tblSettings where id = ?', [id], function(tx, rs){
// do stuff with the resultset.
},
function errorHandler(tx, e){
// do something upon error.
console.warn('SQL Error: ', e);
});
however, I know regular SQL and figured i should be able to request
var arr = [1, 2, 3];
tx.executeSql('SELECT * FROM tblSettings where id in (?)', [arr], function(tx, rs){
// do stuff with the resultset.
},
function errorHandler(tx, e){
// do something upon error.
console.warn('SQL Error: ', e);
});
but that gives us no results, the result is always empty. if i would remove the [arr] into arr, then the sql would get a variable amount of parameters, so i figured it should be [arr]. otherwise it would require us to add a dynamic amount of question marks (as many as there are id's in the array).
so can anyone see what i'm doing wrong?

Answer 1

aparently, there is no other solution, than to manually add a question mark for every item in your array.
this is actually in the specs on w3.org
var q = "";
for each (var i in labels)
q += (q == "" ? "" : ", ") + "?";
// later to be used as such:
t.executeSql('SELECT id FROM docs WHERE label IN (' + q + ')', labels, function (t, d) {
// do stuff with result...
});
more info here: http://www.w3.org/TR/webdatabase/#introduction (at the end of the introduction)
however, at the moment i created a helper function that creates such a string for me
might be better than the above, might not, i haven't done any performance testing.
this is what i use now
var createParamString = function(arr){
return _(arr).map(function(){ return "?"; }).join(',');
}
// when called like this:
createparamString([1,2,3,4,5]); // >> returns ?,?,?,?,?
this however makes use of the underscore.js library we have in our project.

Answer 2

Good answer. It was interesting to read an explanation in the official documentation.
I see this question was answered in 2012. I tried it in Google 37 exactly as it is recommened and this is what I got.
Data on input: (I outlined them with the black pencil)
Chrome complains:
So it accepts as many question signs as many input parameters are given. (Let us pay attention that although array is passed it's treated as one parameter)
Eventually I came up to this solution:
var activeItemIds = [1,2,3];
var q = "";
for (var i=0; i< activeItemIds.length; i++) {
q += '"' + activeItemIds[i] + '", ';
}
q= q.substring(0, q.length - 2);
var query = 'SELECT "id" FROM "products" WHERE "id" IN (' + q + ')';
_db.transaction(function (tx) {
tx.executeSql(query, [], function (tx, results1) {
console.log(results1);
debugger;
}, function (a, b) {
console.warn(a);
console.warn(b);
})
})