Develop Reference

Getting specific value from Array which does not exist in database

I'm trying to get the value or data from the array that doesn't exists in the database.
public Cursor checkExistence(){
Cursor c=null;
String[] values={"headache","cold"};
SQLiteDatabase db= getReadableDatabase();
String query="SELECT * FROM "+TABLE_SYMPTOMS+" WHERE "+COLUMN_SYMP+" IN ("+toArrayRep(values)+")";
c=db.rawQuery(query,null);
Log.i("From Cursor","Cursor Count : " + c.getCount());
if(c.getCount()>0){
String val= c.getString()
Log.i("From Cursor","No insertion");
}else{
Log.i("From Cursor","Insertion");
}
db.close();
return c;
}
public static String toArrayRep(String[] in) {
StringBuilder result = new StringBuilder();
for (int i = 0; i < in.length; i++) {
if (i != 0) {
result.append(",");
}
result.append("'" + in[i] + "'");
}
return result.toString();
}
In the String values={"headache","cold"} ,headache exists but cold does not exist in the database. From the code above, the Cursor returns Count=1 which is count>0 hence i can't insert into table.I would like to know how i can independently check whether the individual data exists, and the one which doesn't exist will be inserted into table.So in this case, "Cold" would be able to be inserted into the table.

If you use a single query to check all values, then what you get is a list of existing values, and you still have to search in the original list for any differences.
It is simpler to check each value individually:
String[] values = { "headache", "cold" };
SQLiteDatabase db = getReadableDatabase();
db.beginTransaction();
try {
for (String value : values) {
long count = DatabaseUtils.queryNumEntries(db,
TABLE_SYMPTOMS, COLUMN_SYMP+" = ?", new String[] { value });
if (count == 0) {
ContentValues cv = new ContentValues();
cv.put(COLUMN_SYMP, value);
db.insert(TABLE_SYMPTOMS, null, cv);
}
}
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}

You need check Cursor.moveToFirst()
True = Have records in cursor.
False = Dont have records.
Example my code:
return database.query( table.getNameTable(),
table.getColumns(),
table.getWhereSelectTableScript(),
null,
table.getGroupBySelectTableScript(),
table.getHavingSelectTableScript(),
table.getOrderBySelectTableScript(),
table.getLimitRecordsSelectTableScript());
See more here !

Sqlite android: Update successful but new row created

Update method returns true.
But when listing the whole table, new rows were created for each update.
ONE table, three columns: PRIMARY_ID, MY_ID, MY_ANOTHER_ID.
I have the following methods:
public void insertOrUpdate(String lStringId){
boolean present= search(lStringId);
if(present){
updateData(lStringId);
} else{
insertData(lStringId);
}
}
Search:
private boolean search(String lStringId) {
Cursor cursor = null;
try {
cursor = mDatabase.query(TABLE_NAME, null,
MY_ID + " = ?", new String[]{lStringId}, null, null, null);
if (null != cursor && cursor.getCount() == 1 && cursor.moveToFirst()) {
return true
}
Log.d(TAG, "-search, cursor.getCount() = " + cursor.getCount());
return false;
} catch (Exception e) {
Log.e(TAG, "-search, Error: "+ e.getLocalizedMessage());
return false;
} finally {
if (null != cursor) {
cursor.close();
cursor = null;
}
}
}
Update:
public boolean updateData(String lStringId) {
Log.d(TAG, " -updateData");
ContentValues lValues = new ContentValues();
lValues.put(MY_ANOTHER_ID, lStringId+"extra");
if (mDatabase.update(TABLE_NAME,
lValues, MY_ID + "= '" + lStringId + "'", null) > 0) {
Log.d(TAG, " -updateData, true");
return true;
}
return false;
}
Insert:
public long insertData(String lStringId) {
Log.d(TAG, " -insertData");
ContentValues dataValues = new ContentValues();
dataValues.put(MY_ID, lStringId);
long result = mDatabase.insert(TABLE_NAME, null, dataValues);
Log.d(TAG, "result: " + result);
return result;
}
After the first new insert, the next time I call insertOrUpdate method, search method returns true. And updateData method was called and it also returns true.
-search, cursor.getCount() = also prints 1.
But when I check the contents of the table, there are two rows with same MY_ID value and different MY_ANOTHER_ID values.
What am I missing?

Lot's of things can go wrong here.
Non atomic operations.
You are first querying whether an object exists then doing the insert or update. In android it's unlikely that another thread will create another object in between these two operations but in other places it can happen so this is a habit to avoid.
Unique key on MY_ID, MY_ANOTHER_ID
If there can only be one MY_ID in that table you should have a unique key on it. If not you should have a together unique key on the my_id, my_another_id pair of columns.
Code in search method.
if (null != cursor && cursor.getCount() == 1
&& cursor.moveToFirst()) {
return true
}
This will return true if there is exactly one record for my_id what if you have two? Then this method will not return true, the calling function will believe there aren't any matching records in that table.
Insert or Update the real deal
Android Sqlite supports ON CONFLICT REPLACE. You can simplify your code a great deal by making use of it.

Android sqlite how to check if a record exists

I would like to check whether a record exists or not.
Here is what I've tried:
MainActivity.class
public void onTextChanged(CharSequence s, int start, int before, int count) {
System.out.println("Ontext changed " + new String(s.toString()));
strDocumentFrom = s.toString();
if(s.toString().isEmpty()){
} else {
try{
strTransactionDate = dbHelper.getTransactionDateByDocumentNumber(strDocumentFrom);
//strTotalAmount = dbHelper.getTotalAmountByDocumentNumber(strDocumentFrom);
//strVan = dbHelper.getVanByDocumentNumber(strDocumentFrom);
//etTransactionDate.setText(strTransactionDate);
//etTotalAmount.setText(strTotalAmount);
//Log.d("Van", "" + strVan);
//etVan.setText(strVan);
} catch (SQLiteException e) {
e.printStackTrace();
Toast.makeText(ReceivingStocksHeader.this,
"Document number does not exist.", Toast.LENGTH_SHORT).show();
}
}
DBHelper.class
// TODO DISPLAYING RECORDS TO TRANSRCVHEADER
public String getTransactionDateByDocumentNumber(String strDocumentNumber){
String[] columns = new String[]{KEY_TRANSACTIONDATE};
Cursor c = myDataBase.query(TBL_INTRANS,
columns, null,
null, null, null, null, null);
if(c != null){
c.moveToFirst();
String date = c.getString(0);
return date;
} else {
Log.d("Error", "No record exists");
}
return null;
}
But it doesn't get it to the catch block to display the toast.
What am I doing wrong in here?

public static boolean CheckIsDataAlreadyInDBorNot(String TableName,
String dbfield, String fieldValue) {
SQLiteDatabase sqldb = EGLifeStyleApplication.sqLiteDatabase;
String Query = "Select * from " + TableName + " where " + dbfield + " = " + fieldValue;
Cursor cursor = sqldb.rawQuery(Query, null);
if(cursor.getCount() <= 0){
cursor.close();
return false;
}
cursor.close();
return true;
}
I hope this is useful to you...
This function returns true if record already exists in db. Otherwise returns false.

These are all good answers, however many forget to close the cursor and database. If you don't close the cursor or database you may run in to memory leaks.
Additionally: You can get an error when searching by String that contains non alpha/numeric characters. For example: "1a5f9ea3-ec4b-406b-a567-e6927640db40". Those dashes (-) will cause an unrecognized token error. You can overcome this by putting the string in an array. So make it a habit to query like this:
public boolean hasObject(String id) {
SQLiteDatabase db = getWritableDatabase();
String selectString = "SELECT * FROM " + _TABLE + " WHERE " + _ID + " =?";
// Add the String you are searching by here.
// Put it in an array to avoid an unrecognized token error
Cursor cursor = db.rawQuery(selectString, new String[] {id});
boolean hasObject = false;
if(cursor.moveToFirst()){
hasObject = true;
//region if you had multiple records to check for, use this region.
int count = 0;
while(cursor.moveToNext()){
count++;
}
//here, count is records found
Log.d(TAG, String.format("%d records found", count));
//endregion
}
cursor.close(); // Dont forget to close your cursor
db.close(); //AND your Database!
return hasObject;
}

Raw queries are more vulnerable to SQL Injection. I will suggest using query() method instead.
public boolean Exists(String searchItem) {
String[] columns = { COLUMN_NAME };
String selection = COLUMN_NAME + " =?";
String[] selectionArgs = { searchItem };
String limit = "1";
Cursor cursor = db.query(TABLE_NAME, columns, selection, selectionArgs, null, null, null, limit);
boolean exists = (cursor.getCount() > 0);
cursor.close();
return exists;
}
Source: here

SELECT EXISTS with LIMIT 1 is much faster.
Query Ex: SELECT EXISTS (SELECT * FROM table_name WHERE column='value' LIMIT 1);
Code Ex:
public boolean columnExists(String value) {
String sql = "SELECT EXISTS (SELECT * FROM table_name WHERE column='"+value+"' LIMIT 1)";
Cursor cursor = database.rawQuery(sql, null);
cursor.moveToFirst();
// cursor.getInt(0) is 1 if column with value exists
if (cursor.getInt(0) == 1) {
cursor.close();
return true;
} else {
cursor.close();
return false;
}
}

You can use SELECT EXISTS command and execute it for a cursor using a rawQuery,
from the documentation
The EXISTS operator always evaluates to one of the integer values 0
and 1. If executing the SELECT statement specified as the right-hand
operand of the EXISTS operator would return one or more rows, then the
EXISTS operator evaluates to 1. If executing the SELECT would return
no rows at all, then the EXISTS operator evaluates to 0.

I have tried all methods mentioned in this page, but only below method worked well for me.
Cursor c=db.rawQuery("SELECT * FROM user WHERE idno='"+txtID.getText()+"'", null);
if(c.moveToFirst())
{
showMessage("Error", "Record exist");
}
else
{
// Inserting record
}

One thing the top voted answer did not mention was that you need single quotes, 'like this', around your search value if it is a text value like so:
public boolean checkIfMyTitleExists(String title) {
String Query = "Select * from " + TABLE_NAME + " where " + COL1 + " = " + "'" + title + "'";
Cursor cursor = database.rawQuery(Query, null);
if(cursor.getCount() <= 0){
cursor.close();
return false;
}
cursor.close();
return true;
}
Otherwise, you will get a "SQL(query) error or missing database" error like I did without the single quotes around the title field.
If it is a numeric value, it does not need single quotes.
Refer to this SQL post for more details

SQLiteDatabase sqldb = MyProvider.db;
String Query = "Select * from " + TABLE_NAME ;
Cursor cursor = sqldb.rawQuery(Query, null);
cursor.moveToLast(); //if you not place this cursor.getCount() always give same integer (1) or current position of cursor.
if(cursor.getCount()<=0){
Log.v("tag","if 1 "+cursor.getCount());
return false;
}
Log.v("tag","2 else "+cursor.getCount());
return true;
if you not use cursor.moveToLast();
cursor.getCount() always give same integer (1) or current position of cursor.

Code :
private String[] allPushColumns = { MySQLiteHelper.COLUMN_PUSH_ID,
MySQLiteHelper.COLUMN_PUSH_TITLE, MySQLiteHelper.COLUMN_PUSH_CONTENT, MySQLiteHelper.COLUMN_PUSH_TIME,
MySQLiteHelper.COLUMN_PUSH_TYPE, MySQLiteHelper.COLUMN_PUSH_MSG_ID};
public boolean checkUniqueId(String msg_id){
Cursor cursor = database.query(MySQLiteHelper.TABLE_PUSH,
allPushColumns, MySQLiteHelper.COLUMN_PUSH_MSG_ID + "=?", new String [] { msg_id }, null, null, MySQLiteHelper.COLUMN_PUSH_ID +" DESC");
if(cursor.getCount() <= 0){
return false;
}
return true;
}

Here's a simple solution based on a combination of what dipali and Piyush Gupta posted:
public boolean dbHasData(String searchTable, String searchColumn, String searchKey) {
String query = "Select * from " + searchTable + " where " + searchColumn + " = ?";
return getReadableDatabase().rawQuery(query, new String[]{searchKey}).moveToFirst();
}

because of possible data leaks best solution via cursor:
Cursor cursor = null;
try {
cursor = .... some query (raw or not your choice)
return cursor.moveToNext();
} finally {
if (cursor != null) {
cursor.close();
}
}
1) From API KITKAT u can use resources try()
try (cursor = ...some query)
2) if u query against VARCHAR TYPE use '...' eg. COLUMN_NAME='string_to_search'
3) dont use moveToFirst() is used when you need to start iterating from beggining
4) avoid getCount() is expensive - it iterates over many records to count them. It doesn't return a stored variable. There may be some caching on a second call, but the first call doesn't know the answer until it is counted.

Try to use cursor.isNull method.
Example:
song.isFavorite = cursor.isNull(cursor.getColumnIndex("favorite"));

You can use like this:
String Query = "Select * from " + TABLE_NAME + " where " + Cust_id + " = " + cust_no;
Cursor cursorr = db.rawQuery(Query, null);
if(cursor.getCount() <= 0){
cursorr.close();
}
cursor.close();

private boolean checkDataExistOrNot(String columnName, String value) {
SQLiteDatabase sqLiteDatabase = getReadableDatabase();
String query = "SELECT * FROM" + TABLE_NAME + " WHERE " + columnName + " = " + value;
Cursor cursor = sqLiteDatabase.rawQuery(query, null);
if (cursor.getCount() <= 0) {
cursor.close();
return false; // return false if value not exists in database
}
cursor.close();
return true; // return true if value exists in database
}

I prefer to do it this way because it's fast and less expensive than other methods:
Cursor cursor = db.rawQuery("SELECT 1 FROM table WHERE condition = 1 LIMIT 1", null);
try {
if (cursor.moveToNext()) {
//Record exists
} else {
//Record doesn't exists
}
} finally {
cursor.close();
}

My version:
public boolean isTitleExists(String title, String type) {
int isExists = 0;
try {
String query = "SELECT EXISTS (SELECT 1 FROM titles WHERE title = ? and type = ?)";
PreparedStatement statement = connection.prepareStatement(query);
statement.setString(1, title);
statement.setString(2, type);
ResultSet rs = statement.executeQuery();
rs.next();
isExists = rs.getInt(1);
rs.close();
statement.close();
} catch (SQLException e) {
Common.console("isTitleExists error: " + e.getMessage());
}
return isExists == 1;
}

Handling Invalid SQLite Queries in Android

I have a simple code that manages to successfully query an SQLite Database and convert that result from cursor to string in order to display it on screen.
My problem now would be invalid queries that make the App Crash. Would there be a way to successfully handle invalid queries? Preferably something that would keep my app from crashing and would just redirect the user to the home page and display a toast of warning.
So far my method for searching looks like this:
public String search(DataBaseHelper myDB){
SQLiteDatabase db = myDB.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT BuildingColor, Room FROM LSBuildingsDB WHERE _id =" + newString, null);
cursor.moveToFirst();
String data = cursor.getString(cursor.getColumnIndexOrThrow("BuildingColor")) + " " +
cursor.getString(cursor.getColumnIndex("Room"));
//Toast msg = Toast.makeText(getBaseContext(),data, Toast.LENGTH_SHORT);
//msg.show();
cursor.close();
return data;
}

Cursor cursor = NULL ;
try
{
cursor = db.rawQuery("SELECT BuildingColor, Room FROM LSBuildingsDB WHERE _id =" + newString, null);
if(cursor != NULL)
{
try {
if (cursor.moveToNext()) {
String data = cursor.getString(cursor.getColumnIndexOrThrow("BuildingColor")) +
" " + cursor.getString(cursor.getColumnIndex("Room"));
} else {
// Query result was empty, deal with it here.
}
} finally {
// Cursors should be closed
cursor.close();
}
}
}
catch (SQLiteException e) // (Exception e) catch-all:s are bad mmkay.
{
//print exception
}

Cursor cursor = null;
String data = "";
try
{
cursor = db.rawQuery("SELECT BuildingColor, Room FROM LSBuildingsDB WHERE _id =" + newString, null);
}catch (Exception e) {
// TODO: handle exception
}

Checking if a column exists in an application database in Android

Is there a nice way in Android to see if a column exists in a table in the application database? (I know there are questions similar to this one already, but there don't seem to be any that are Android specific.)

cursor.getColumnIndex(String columnName) returns -1 if, the column doesn't exist. So I would basically perform a simple query like "SELECT * FROM xxx LIMIT 0,1" and use the cursor to determine if the column, you are looking for, exists
OR
you can try to query the column "SELECT theCol FROM xxx" and catch an exception

My function based on #martinpelants answer:
private boolean existsColumnInTable(SQLiteDatabase inDatabase, String inTable, String columnToCheck) {
Cursor mCursor = null;
try {
// Query 1 row
mCursor = inDatabase.rawQuery("SELECT * FROM " + inTable + " LIMIT 0", null);
// getColumnIndex() gives us the index (0 to ...) of the column - otherwise we get a -1
if (mCursor.getColumnIndex(columnToCheck) != -1)
return true;
else
return false;
} catch (Exception Exp) {
// Something went wrong. Missing the database? The table?
Log.d("... - existsColumnInTable", "When checking whether a column exists in the table, an error occurred: " + Exp.getMessage());
return false;
} finally {
if (mCursor != null) mCursor.close();
}
}
Simply call:
boolean bla = existsColumnInTable(myDB,"MyTable","myColumn2check");

I actually wrote this function that seems pretty clean:
private boolean field_exists( String p_query )
{
Cursor mCursor = mDb.rawQuery( p_query, null );
if ( ( mCursor != null ) && ( mCursor.moveToFirst()) )
{
mCursor.close();
return true ;
}
mCursor.close();
return false ;
}
I call it like this:
if ( field_exists( "select * from sqlite_master "
+ "where name = 'mytable' and sql like '%myfield%' " ))
{
do_something ;
}

Here is my solution to the issue which adds to flexo's solution a little.
You can put this method in any class, perhaps your SQLiteOpenHelper extending class.
public static boolean columnExistsInTable(SQLiteDatabase db, String table, String columnToCheck) {
Cursor cursor = null;
try {
//query a row. don't acquire db lock
cursor = db.rawQuery("SELECT * FROM " + table + " LIMIT 0", null);
// getColumnIndex() will return the index of the column
//in the table if it exists, otherwise it will return -1
if (cursor.getColumnIndex(columnToCheck) != -1) {
//great, the column exists
return true;
}else {
//sorry, the column does not exist
return false;
}
} catch (SQLiteException Exp) {
//Something went wrong with SQLite.
//If the table exists and your query was good,
//the problem is likely that the column doesn't exist in the table.
return false;
} finally {
//close the db if you no longer need it
if (db != null) db.close();
//close the cursor
if (cursor != null) cursor.close();
}
}

If you use ActiveAndroid
public static boolean createIfNeedColumn(Class<? extends Model> type, String column) {
boolean isFound = false;
TableInfo tableInfo = new TableInfo(type);
Collection<Field> columns = tableInfo.getFields();
for (Field f : columns) {
if (column.equals(f.getName())) {
isFound = true;
break;
}
}
if (!isFound) {
ActiveAndroid.execSQL("ALTER TABLE " + tableInfo.getTableName() + " ADD COLUMN " + column + " TEXT;");
}
return isFound;
}

At the risk of just posting the same solution but shorter. Here's a cut down version based on #flexo's
private boolean doesColumnExistInTable(SupportSQLiteDatabase db, String tableName, String columnToCheck) {
try (Cursor cursor = db.query("SELECT * FROM " + tableName + " LIMIT 0", null)) {
return cursor.getColumnIndex(columnToCheck) != -1;
} catch (Exception Exp) {
// Something went wrong. we'll assume false it doesn't exist
return false;
}
}
And in Kotlin
private fun doesColumnExistInTable(db: SupportSQLiteDatabase, tableName: String, columnToCheck: String): Boolean {
try {
db.query("SELECT * FROM $tableName LIMIT 0", null).use { cursor -> return cursor.getColumnIndex(columnToCheck) != -1 }
} catch (e: Exception) {
// Something went wrong. we'll assume false it doesn't exist
return false
}
}

this is my testing code:
String neadle = "id"; //searched field name
String tableName = "TableName";
boolean found = false;
SQLiteDatabase mDb = ActiveAndroid.getDatabase();
Cursor mCursor = mDb.rawQuery( "SELECT * FROM sqlite_master WHERE name = '"+tableName+"' and sql like '%"+neadle+"%'" , null);
mCursor.moveToFirst();
String fie = ",";
if (mCursor.getCount() > 0) {
String[] fields = mCursor.getString(mCursor.getColumnIndex("sql")).split(",");
for (String field: fields) {
String[] fieldNameType = field.trim().split(" ");
if (fieldNameType.length > 0){
fie += fieldNameType[0]+",";
}
}
}else {
//table not exist!
}
if (mCursor != null) mCursor.close();
// return result:
found = fie.contains(","+neadle+",");