CODEWITHSUNDEEP
javaandroidsqlitecsv
John
John

Reputation: 5

Exporting multiple tables to multiple CSV files

I have many tables in my database in the app. During the app use, these tables are created by the user and also their names.

I would like to export all tables, each one to a single .CSV file with the table's name.

For example, I have 3 tables named 1, 2 and 3. I would like to export and them create files 1.csv, 2.csv and 3.csv.

I really appreciate some help, because I could not find any answer in the web.

I am using some classes called CSVReader and CSVWriter, which are very popular.

Here in my method to export. It does not show any error, but no file is exported:

public void exportTables (View view) {
    File dbFile = getDatabasePath("database.db");
    Banco dbhelper = new Banco(getApplicationContext());
    File exportDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
    if (!exportDir.exists()) {
        exportDir.mkdirs();
    }

    File file = new File(exportDir, tableName +".csv");

    try {

        file.createNewFile();
        CSVWriter csvWriter = new CSVWriter(new FileWriter(file));
        SQLiteDatabase db = dbhelper.getReadableDatabase();
        Cursor curCSV = db.rawQuery("SELECT * FROM sqlite_master WHERE type='table' AND name NOT LIKE 'android_metadata' AND name NOT LIKE 'sqlite_sequence'", null);
        csvWriter.writeNext(curCSV.getColumnNames());

        while(curCSV.moveToNext()) {
            // Table columns
            String arrStr[] ={curCSV.getString(0),curCSV.getString(1)};
            csvWriter.writeNext(arrStr);
        }

        csvWriter.close();

        curCSV.close();
    }
    catch(Exception sqlEx) {
        Log.e("MainActivity", sqlEx.getMessage(), sqlEx);
    }

    Toast.makeText(this, "FILE EXPORTED WITH SUCCESS!", Toast.LENGTH_SHORT).show();
}

Upvotes: 0

Views: 1832

Answers (1)

Bentaye
Bentaye

Reputation: 9766

This actually a 2 steps process:

1 - List table names

Your first query 

SELECT * 
FROM sqlite_master 
WHERE type='table' 
AND name NOT LIKE 'android_metadata' 
AND name NOT LIKE 'sqlite_sequence'

returns a list of tables and looks like this 

type  |  name  | tbl_name | rootpage |       sql        |
------+--------+----------+----------+------------------+
table | table1 |  table1  |     2    | CREATE TABLE ... |
table | table2 |  table2  |     2    | CREATE TABLE ... |
table | table3 |  table3  |     2    | CREATE TABLE ... |

You could simply return the names instead of all the columns

SELECT name
FROM sqlite_master 
WHERE type='table' 
AND name NOT LIKE 'android_metadata' 
AND name NOT LIKE 'sqlite_sequence'

You need to read each row to get table names

2 - Then for each table you need create a file and query the table, ex:

SELECT * FROM table1

Then stick these in your file

CODE:

I did not test that code but you should be able to make it work:

This first method will list the table names 

private static List<String> listTables(SQLiteDatabase db) {
    List<String> tableNames = new ArrayList<>();

    Cursor tableListCursor = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'android_metadata' AND name NOT LIKE 'sqlite_sequence'", null);
    while(tableListCursor.moveToNext()) {
        // get the name of the table
        tableNames.add(tableListCursor.getString(0));
    }
    tableListCursor.close();

    return tableNames;
}

This second method will dump a table to a file 

private static void dumpTableToCsvFile(SQLiteDatabase db, String tableName) {
    try {
        // Query the data in the table
        Cursor cursor = db.rawQuery("SELECT * FROM " + tableName, null);

        File file = new File(exportDir, tableName +".csv");
        file.createNewFile();

        CSVWriter csvWriter = new CSVWriter(new FileWriter(file));
        // Write the table data to the file
        csvWriter.writeNext(cursor.getColumnNames());
        while(cursor.moveToNext()) {
            String arrStr[] = { cursor.getString(0), cursor.getString(1) };
            csvWriter.writeNext(arrStr);
        }
        // close cursor and writer
        cursor.close();
        csvWriter.close();

    } catch (IOException e) {
        // handle exception
    }
}

And you use them this way:

SQLiteDatabase db = dbhelper.getReadableDatabase();
List<String> tableNames = listTables(db);
for(String tableName : tableNames) {
    dumpTableToCsvFile(db, tableName);
}

Upvotes: 1

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