How to change the dataType of a column from text to int with GRDB

Question

I have my database pre-created and it gets loaded to the apps documents directory on the initial launch. I use DB Browser for SQLite

In the database I have a table x with a column y. The column dataType is set to accept text and is currently empty. The column is there but was not used on earlier versions of the app.

I want to begin using the column but I want it to hold an Int rather than text.

How do I change the DataType of the column in GRDB?

// MARK: - Set the Default Value for the Grade Picker
    func setDefaultValue(item: String, inComponent: Int)
    {
        if let indexPosition = K.Grading_Array.array.firstIndex(of: item)
        {
            picker_Outlet.selectRow(indexPosition, inComponent: inComponent, animated: false)
        }
    }
    
    // MARK: - Done Btn Tapped (Grade)
    @IBAction func pickerDoneBtn_Tapped(_ sender: UIButton)
    {
        backgroundView_Outlet.isHidden = true
        
        // Hide the picker
        UIView.animate(withDuration: 0.5, animations: { [weak self] in
            self?.gradePickerView_Outlet.alpha = 0
        })
        
        if let index = K.Grading_Array.array.firstIndex(of: selectedGrade)
        {
            do {
                try dbQueue_GRDB.write { db in
                    try db.execute(sql: "UPDATE My_Settings SET Default_Grade = :default_Grade WHERE Settings_ID = :id",
                                   arguments: ["default_Grade": index, "id": 1])
                }
                
            } catch  {
                print("Updating the default grade failed! \(VC_String) \(error)")
            }
        }
    }
    
    // MARK: - Grade Fld Tapped
    @IBAction func gradeFld_Tapped(_ sender: TextField_Designable)
    {
        sender.resignFirstResponder()
        backgroundView_Outlet.isHidden = false
        let gradeInt = ModelData.getThe_Default_Grade()
        
        setDefaultValue(item: K.Grading_Array.array[gradeInt], inComponent: 0)
        
        // Show the picker
        UIView.animate(withDuration: 0.5, animations: { [weak self] in
            self?.gradePickerView_Outlet.alpha = 1
        })
    }


// MARK: - Get the Default_Grade
    static func getThe_Default_Grade() -> Int
    {
        var theGrade: Int = 0
        
        do {
            let settings = try dbQueue_GRDB.read { db in
                try My_Settings.fetchOne(db)
            }
            theGrade = settings?.Default_Grade ?? 0
        } catch {
            print("Getting the isAnimation Status failed: (\(VC_StringX)) \(error)")
        }
        
        return theGrade
    }

Answer 1

SQLite does not support such table alteration (changing the type of a column) out of the box. In order to change the type of a column, you need to recreate the table.

To do so:

If your app is using GRDB migrations, follow closely the instructions documented by GRDB, at https://github.com/groue/GRDB.swift/blob/master/Documentation/Migrations.md#advanced-database-schema-changes

If your app is not using GRDB migrations: follow closely the instructions documented by SQLite, at https://www.sqlite.org/lang_altertable.html#making_other_kinds_of_table_schema_changes