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.