Android Tutorial SQL tutorial

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nemethv

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Hello,

I'm struggling with reading stuff from an sqlite db file that I've already created outside the app. The file doesn't need to be edited/modified/etc in the app.
Im trying to open the file, but the code SQL1.Initialize(File.DirAssets,"lineinfo.db",False) - fails, I get an errormessage on this when trying to do it saying "database not available". The file is in the files tab. SQL is enabled/ticked.

The overall aim would be to create a list with information extracted from the SQL file.
In theory, it would be something like:

B4X:
Sub Globals

   Dim LineList As ListView
   Dim SQL1 As SQL
   Dim Cursor1 As Cursor ' not sure what to do with this?
End Sub


Sub Activity_Create(FirstTime As Boolean)
   
   Activity.Color = Colors.white
   If SQL1.IsInitialized = False Then 
      SQL1.Initialize(File.DirAssets,"lineinfo.db",False) ' this one fails
   End If   
   
    
   LineList.Initialize("LineList")
   LineList.Visible=True:LineList.Clear
   
   LineList.AddSingleLine(SQL1.ExecQuerySingleResult("SELECT DISTINCT LineName FROM lineinfo")) 'dont think this works either, but you get the gist of what i need hopefully...
   
   
    Activity.AddView(LineList, 0, 0, 100%x, 100%y)
End Sub
At the end I'd like the list to return results like "Line A", "Line B"...
Any thoughts?

Thank you

ps. i might not reply until the end of the coming long weekend, but I'll do my best to do so.
 
Last edited:

Erel

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You cannot open a database in the assets folder. This is a virtual read-only folder located inside the APK file. You will need to first copy the database to a writable location. You can use DBUtils for that task.
 

nemethv

Member
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You cannot open a database in the assets folder. This is a virtual read-only folder located inside the APK file. You will need to first copy the database to a writable location. You can use DBUtils for that task.
Thanks! Worked :)
 
Last edited:

zekigultekin

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How can add SQL library to my basic4android project

Dear Erel,
I want use SQL in my project. When I define Dim SQL1 as SQL then I cannot see SQL reference. ;)

How can I add SQL library reference to my project.

Best regards,
 

Erel

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You should go the Libraries tab (right side of the IDE) and check SQL.
 

McJaegs

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So I have my database created, but where in my project folder do I need to place it in order for it to be accessed?

I am also trying to populate a spinner with unique values from one column of the database. What would be the code to do that? Right now I have this

Cursor1 = RadioSQL.ExecQuery("SELECT DISTINCT Genre From Chicago")

If CitySpinner.SelectedItem = "Chicago" Then
GenreSpinner.AddAll(Cursor1)
 
Last edited:

McJaegs

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I recommend you to use DBUtils: Basic4android Search: DBUtils

It will help you put the database in the correct folder and it also includes an ExecuteSpinner method.
Ok, thanks. I have that now, but now when I try to run my program I get the error: java.lang.ClassCastException:android.database.sqlite.SQLiteCursor

I'm not sure what is causing this.
 

Erel

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Run your program in Debug mode and check the full error message in the logs.
 

nemethv

Member
Licensed User
Hi,

I'm trying to simplify a piece of code that i've been using.
The code I'm doing now is:
B4X:
LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever&"')
   For i = 1 To LocalLineCount
      LocalLineList.AddSingleLine(SQL1.ExecQuerySingleResult("SELECT DISTINCT LineName FROM lineinfo WHERE LocalLineID = " & i ))
   Next
I was wondering if there is any way to replace the last part (&i) with something auto-incremental because at the moment I have to put zillions of various IDs into my data tables rather than just actually somehow saying, "select the next line after the one you've already selected".
In other terms, what I'm trying to achieve is that there are certain stations on the underground network that serve more than one line. Rather than having to assign an ID for each line on each station and then call the LocalLineID as above, I want to avoid and automate that process somehow. Is it possible?
Thanks
 
Last edited:

poseidon

Member
Licensed User
re

I couldnt understand exactly... but you can make it one (?)

LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever& "' and
LocalLineID = " & i)

or something like :

LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever& "' and
LocalLineID > " & i)

(?)
 

nemethv

Member
Licensed User
I couldnt understand exactly... but you can make it one (?)

LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever& "' and
LocalLineID = " & i)

or something like :

LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever& "' and
LocalLineID > " & i)

(?)
I'm hoping avoid having having to use IDs in general. What I'd like is that if we know that the distinct count of stations is say 7 and then in a command I say select distinct stations, then I'd get 7 names. Then I'd want to return the first, second, nth. (rather having a prefixed ID value)
 

poseidon

Member
Licensed User
B4X:
LocalLineCount = SQL1.ExecQuerySingleResult("SELECT count(DISTINCT LineName) FROM lineinfo Where StationName = '"&whatever&"')


'forget this    For i = 1 To LocalLineCount
       Cursor=SQL1.ExecQuery("SELECT DISTINCT LineName FROM lineinfo WHERE (LocalLineID > 0 and  LocalLineID <" & LocalLineCount+1 & ")")
'forget this    Next

^so only 2SQL will be executed but then you have to make a loop to add at listview

for i=0 to  Cursor.Count-1
 LocalLineList.AddSingleLine(Coursor.GetString2(0))
next

for sure is more faster.


Generic Cursor Sample :
B4X:
   Dim SQLReader As Cursor
   Dim i As Int
    SQLReader = SQL1.ExecQuery("SELECT id,Code, Name FROM CONTACTS order by Name")

    For i = 0 To SQLReader.RowCount - 1
        SQLReader.Position = i
      
      lstv.AddTwoLines2(SQLReader.GetString("Code"),SQLReader.GetString("Name"),SQLReader.GetString("id"))
    Next
    SQLReader.Close
 
Last edited:

nemethv

Member
Licensed User
Found it

B4X:
For a = 0 To LineCount -1
   CurrentLineName = SQL1.ExecQuerySingleResult("SELECT DISTINCT LineName FROM LineInfo ORDER BY LineName LIMIT 1 OFFSET " & a)
Next
 

ltrebuchet

Member
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Dir.Assets

My DBFile is included within the Files of my project, but it is not found File.DirAssets.
What did I miss?
Thank You
 

jeeradate

Member
Licensed User
Question relate to Cursor read data

From the code of the example as below

B4X:
Sub LogTable1
    Dim Cursor1 As Cursor
    Cursor1 = SQL1.ExecQuery("SELECT col1, col2, col3 FROM table1")
    For i = 0 To Cursor1.RowCount - 1
        Cursor1.Position = i
        Log("************************")
        Log(Cursor1.GetString("col1"))
        Log(Cursor1.GetInt("col2"))
        Log(Cursor1.GetInt("col3"))
    Next
    Cursor1.Close
End Sub
The code "Cursor1 = SQL1.ExecQuery("SELECT col1, col2, col3 FROM table1")" read all the records in the table and store in "Cursor1" or read nothing
or read one record with this code "Cursor1.Position = i"

Would be kind to advice me?
:sign0104:
 

klaus

Expert
Licensed User
Cursor1 = SQL1.ExecQuery("SELECT col1, col2, col3 FROM table1")
Reads col1, col2 and col3 from all records in the database and stores them in the Cursor1 object.

Cursor1.RowCount
Holds the number of records (rows).

Cursor1.Position = i
Sets the index of the record (row), the first index = 0.

Cursor1.GetString("col1")
Gets the value of column col1 for the given row in Cursor1.Position = i.

Did you have a look at chapter 3 SQLite Database in the User's Guide ?

Best regards.
 

jeeradate

Member
Licensed User
Thank you for your kind response.

Both Guide is very helpful for me.
Thank you for your hard work of making these Guide.
:sign0098:
 
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