Android Question DBUtils.ExecuteMap crashes

TrisectDevelopment · Nov 26, 2015

I'm using DBUtils.ExecuteMap to get an ID from the database like this.

B4X:

findID = DBUtils.ExecuteMap(SQL, "SELECT ID FROM GemteLokationer ORDER BY ID DESC", Null)

I use this to get the newest ID and increment it for the next post.

The first time I run this where the App create the database and table it works okay.
But when delete all posts in the table and start the App again i crasches.

It crasches in DBUtil on line 214

B4X:

cur = SQL.ExecQuery(Query)

Is there method to check if a table is empty?
Or another way to do what I do?

P.S.
I deleted the posts in a SQLIte App on the phone not in my App.

Mahares · Nov 26, 2015

TrisectDevelopment said:
Is there method to check if a table is empty?

B4X:

Query="SELECT * FROM GemteLokationer"
    cur = SQL.ExecQuery(Query)
    If Cur.RowCount=0 Then
        Msgbox("Table is empty","")
    End If

TrisectDevelopment · Nov 26, 2015

Mahares said:

B4X:

Query="SELECT * FROM GemteLokationer"
    cur = SQL.ExecQuery(Query)
    If Cur.RowCount=0 Then
        Msgbox("Table is empty","")
    End If

Does that work with DBUtils?

Mahares · Nov 26, 2015

TrisectDevelopment said:
Does that work with DBUtils?

That is part of SQLite native commands. DBUtils will not interfere with it. You will be fine.

TrisectDevelopment · Nov 26, 2015

Your code works just fine thanks.

But I found out that the problem was because I did not initialize SQL.
So both ways to do it works now.

klaus · Nov 26, 2015

To get the number of rows in a table you can use this:

B4X:

Dim RowNb As Int
RowNb = SQL1.ExecQuerySingleResult("SELECT count(*) FROM GemteLokationer")

If the table is empty the result is 0.

To get the highest rowID from a table you can use this:

B4X:

Dim MaxRowID As Long
MaxRowID = SQL1.ExecQuerySingleResult(SELECT "max(rowID) FROM GemteLokationer")

If the table is empty this will through an error, you must check if the table is empty.

B4X:

Dim RowNb As Int
Dim MaxRowID = 0 As Long
RowNb = Starter.SQL1.ExecQuerySingleResult("SELECT count(*) FROM Stock")
If RowNb > 0 Then
   MaxRowID = Starter.SQL1.ExecQuerySingleResult("SELECT max(rowID) FROM Stock")
End If

Android Question DBUtils.ExecuteMap crashes

TrisectDevelopment

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