I have done a lot of research and was unable to find a suitable method to delete all the tables in an SQLite database. Finally, I did a code to get all table names from the database and I tried to delete the tables using the retrieved table names one by one. It didn't work as well.
Please suggest me a method to delete all tables from the database.
This is the code that I used:
public void deleteall(){
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
do
{
db.delete(c.getString(0),null,null);
}while (c.moveToNext());
}
function deleteall()
is called on button click whos code is given as below:
public void ButtonClick(View view)
{
String Button_text;
Button_text = ((Button) view).getText().toString();
if(Button_text.equals("Delete Database"))
{
DatabaseHelper a = new DatabaseHelper(this);
a.deleteall();
Toast.makeText(getApplicationContext(), "Database Deleted Succesfully!", Toast.LENGTH_SHORT).show();
}}
You can remove an entire table using the DROP TABLE statement. You just need to specify the name of the table you need to delete.
SQLite allows you to drop only one table at a time. To remove multiple tables, you need to issue multiple DROP TABLE statements. If you remove a non-existing table, SQLite issues an error.
Use DROP TABLE
:
// query to obtain the names of all tables in your database
Cursor c = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
List<String> tables = new ArrayList<>();
// iterate over the result set, adding every table name to a list
while (c.moveToNext()) {
tables.add(c.getString(0));
}
// call DROP TABLE on every table name
for (String table : tables) {
String dropQuery = "DROP TABLE IF EXISTS " + table;
db.execSQL(dropQuery);
}
Tim Biegeleisen's answer almost worked for me, but because I used AUTOINCREMENT
primary keys in my tables, there was a table called sqlite_sequence
. SQLite would crash when the routine tried to drop that table. I couldn't catch the exception either. Looking at https://www.sqlite.org/fileformat.html#internal_schema_objects, I learned that there could be several of these internal schema tables that I shouldn't drop. The documentation says that any of these tables have names beginning with sqlite_ so I wrote this method
private void dropAllUserTables(SQLiteDatabase db) {
Cursor cursor = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
//noinspection TryFinallyCanBeTryWithResources not available with API < 19
try {
List<String> tables = new ArrayList<>(cursor.getCount());
while (cursor.moveToNext()) {
tables.add(cursor.getString(0));
}
for (String table : tables) {
if (table.startsWith("sqlite_")) {
continue;
}
db.execSQL("DROP TABLE IF EXISTS " + table);
Log.v(LOG_TAG, "Dropped table " + table);
}
} finally {
cursor.close();
}
}
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