CODEWITHSUNDEEP
qtsqlitelocal-storageqmlqtquick2
marmistrz
marmistrz

Reputation: 6404

SELECT COUNT(*) doesn't work in QML

I'm trying to get the number of records with QML LocalStorage, which uses sqlite. Let's take this snippet in account:

function f() {
    var db = LocalStorage.openDatabaseSync(...)

    db.transaction (
        function(tx) {
            var b = tx.executeSql("SELECT * FROM t")
            console.log(b.rows.length)
            var  c = tx.executeSql("SELECT COUNT(*) FROM t")
            console.log(JSON.stringify(c))
        }
        )
}

The output is:

qml: 3
qml: {"rowsAffected":0,"insertId":"","rows":{}}

What am I doing wrong that the SELECT COUNT(*) doesn't output anything?

EDIT: rows only seems empty in the second command. Calling

console.log(JSON.stringify(c.rows.item(0)))

gives

qml: {"COUNT(*)":3}

Two questions now:

  1. Why is rows shown as empty
  2. How can I access the property inside c.rows.item(0)

Upvotes: 3

Views: 482

Answers (1)

skypjack
skypjack

Reputation: 50550

In order to visit the items, you have to use:

b.rows.item(i)

Where i is the index of the item you want to get (in your first example, i belongs to [0, 1, 2] for you have 3 items, in the second one it is 0 and you can query it as c.rows.item(0)).

The rows field appears empty and it is a valid result, for the items are not part of the rows field itself (indeed you have to use a method to get them, as far as I know that method could also be a memento that completely enclose the response data) and the item method is probably defined as not enumerable (I cannot verify it, I'm on the beach and it's quite difficult to explore the Qt code now :-)). You can safely rely on the length parameter to know if there are returned values, thus you can iterate over them to print them out. I did something like that in a project of mine and it works fine.

The properties inside item(0) have the same names given for the query. I suggest to rewrite that query as:

select count(*) as cnt from t

Then, you can get the count as:

c.rows.item(0).cnt

Upvotes: 6

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