iOS Sqlite3 Delete Query Not Deleting Row - iphone

Question

I am using this code to delete a row from the database for my ipad application,
-(BOOL) removeSegmentWithSegmentId:(NSInteger)sId
{
AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
sqlite3_stmt *statement;
NSString *removeKeyword =[NSString stringWithFormat:#"DELETE FROM segment WHERE segment.segment_id = %d",sId];
const char *query = [removeKeyword UTF8String];
NSLog(#"%#",removeKeyword);
//if(sqlite3_prepare_v2(appDelegate->globalConnection,[removeKeyword UTF8String] , -1, &statement, NULL) == SQLITE_OK)
if(sqlite3_prepare_v2(appDelegate->globalConnection,query , -1, &statement, NULL) == SQLITE_OK)
{
if(sqlite3_step(statement) == SQLITE_DONE) {
sqlite3_finalize(statement);
return YES;
}
}
return NO;
}
but it is not working, can anyone guide me please?

Answer 1

Is your method returning YES?
A couple of things:
Always log sqlite3_errmsg on any failures
Right now, you're only doing sqlite3_finalize is sqlite3_step returns SQLITE_DONE, whereas you really should be doing it whenever you successfully did sqlite3_prepare_v2
So, I might suggest, at a minimum:
-(BOOL) removeSegmentWithSegmentId:(NSInteger)sId
{
BOOL success = NO;
AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
sqlite3_stmt *statement;
NSString *removeKeyword = [NSString stringWithFormat:#"DELETE FROM segment WHERE segment.segment_id = %d",sId];
if (sqlite3_prepare_v2(appDelegate->globalConnection, [removeKeyword UTF8String], -1, &statement, NULL) == SQLITE_OK)
{
if(sqlite3_step(statement) == SQLITE_DONE)
{
success = YES;
}
else
{
NSLog(#"%s: step not ok: %s", __FUNCTION__, sqlite3_errmsg(appDelegate->globalConnection));
}
sqlite3_finalize(statement);
}
else
{
NSLog(#"%s: prepare failure: %s", __FUNCTION__, sqlite3_errmsg(appDelegate->globalConnection));
}
return success;
}
Assuming this method was always returning YES, if you're not seeing records deleted, it must be that it's not finding a record to delete. (That is not considered a SQLite failure. The SQL was successfully executed, but the WHERE clause couldn't be satisfied.) You can verify this by defining the following method:
- (NSInteger)countSegmentWithSegmentId:(NSInteger)sId
{
NSInteger count = 0;
AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
sqlite3_stmt *statement;
NSString *sql = [NSString stringWithFormat:#"SELECT segment_id FROM segment WHERE segment.segment_id = %d", sId];
if (sqlite3_prepare_v2(appDelegate->globalConnection, [sql UTF8String], -1, &statement, NULL) == SQLITE_OK)
{
while ((rc = sqlite3_step(statement)) == SQLITE_ROW)
count++;
sqlite3_finalize(statement);
}
else
{
NSLog(#"%s: prepare failure: %s", __FUNCTION__, sqlite3_errmsg(appDelegate->globalConnection));
return -1;
}
return count;
}
And then put the diagnostic message in removeSegmentWithSegmentId:
- (BOOL)removeSegmentWithSegmentId:(NSInteger)sId
{
BOOL success = NO;
NSInteger count = [self countSegmentWithSegmentId:sId];
NSLog(#"%s there are %d records with segment_id of %d", __FUNCTION__, count, sId);
AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
sqlite3_stmt *statement;
NSString *removeKeyword = [NSString stringWithFormat:#"DELETE FROM segment WHERE segment.segment_id = %d",sId];
if (sqlite3_prepare_v2(appDelegate->globalConnection, [removeKeyword UTF8String], -1, &statement, NULL) == SQLITE_OK)
{
if(sqlite3_step(statement) == SQLITE_DONE)
{
success = YES;
}
else
{
NSLog(#"%s: step not ok: %s", __FUNCTION__, sqlite3_errmsg(appDelegate->globalConnection));
}
sqlite3_finalize(statement);
}
else
{
NSLog(#"%s: prepare failure: %s", __FUNCTION__, sqlite3_errmsg(appDelegate->globalConnection));
}
return success;
}

Answer 2

if(sqlite3_step(statement) == SQLITE_DONE)
{
sqlite3_finalize(statement);
return YES;
}
else
{
NSLog(#"Failed to delete row %s", sqlite3_errmsg(database));
}
check the error msg.

Answer 3

Please try this
Steps are
1.Open database
2.Delete row from table
3.Close database
Also added NSLog to view the error in console
//------------------------------------------------------------------------
// Method : checkAndCreateDatabase
// Method to Check and Create the database
//------------------------------------------------------------------------
//Function to check & create a database
-(void) checkAndCreateDatabase
{
//-------------------------------------------
BOOL success;
NSFileManager *fileManager = [NSFileManager defaultManager];
success = [fileManager fileExistsAtPath:cDatabasePath];
//-------------------------------------------
//databse already there
if(success)
{
return;
}
//-------------------------------------------
//create database
NSString *databasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:cDatabaseName];
[fileManager copyItemAtPath:databasePathFromApp toPath:cDatabasePath error:nil];
}
//------------------------------------------------------------------------
// Method : checkAndCreateDatabase
// Method to open database
//------------------------------------------------------------------------
-(void) openDatabase
{
cDatabaseName = #"db.sqlite";
NSArray *documentsPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDir = [documentsPaths objectAtIndex:0];
cDatabasePath = [documentDir stringByAppendingPathComponent:cDatabaseName];
[self checkAndCreateDatabase];
//-------------------------------------------
if(sqlite3_open([cDatabasePath UTF8String],&database) == SQLITE_OK)
{
//nothing
}
}
//------------------------------------------------------------------------
// Method : closeDatabase
// Method to close database
//------------------------------------------------------------------------
- (void)closeDatabase
{
// Close the database.
if (sqlite3_close(database) != SQLITE_OK) {
//NSLog(#"Error: failed to close database with message '%s'.", sqlite3_errmsg(database));
}
}
-(BOOL) removeSegmentWithSegmentId:(NSInteger)sId
{
//for sharing variables of appdelegate file
AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
BOOL isDeleted=NO;
[self openDatabase];
const char *sqlStatement;
sqlStatement = "DELETE FROM segment WHERE segment_id =?";
sqlite3_stmt *compiledStatement;
if(sqlite3_prepare_v2(appDelegate.database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK)
{
sqlite3_bind_int(compiledStatement, 1, sId);
if(SQLITE_DONE != sqlite3_step(compiledStatement))
{
NSLog( #"Error while deleting metadata of segment '%s'", sqlite3_errmsg(appDelegate.database));
}
else
{
NSLog(#"Deleted chart segment successfully !");
isDeleted=YES;
}
//-------------------------------------------
sqlite3_reset(compiledStatement);
}
else
{
NSLog( #"Error while deleting segment of chart '%s'", sqlite3_errmsg(appDelegate.database));
}
sqlite3_finalize(compiledStatement);
[self closeDatabase];
return isDeleted;
}

Answer 4

delete rows using name from text box.
(BOOL) deleteRow:(NSString *)name {
const char *dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath, &database) == SQLITE_OK) {
NSString *querySQL = [NSString stringWithFormat: #"DELETE FROM person WHERE name='%#'",name];
const char *query_stmt = [querySQL UTF8String];
if (sqlite3_prepare_v2(database, query_stmt, -1, &statement, NULL) == SQLITE_OK) {
if (sqlite3_step(statement) == SQLITE_DONE) {
sqlite3_finalize(statement);
sqlite3_close(database);
return YES;
}
else
{
NSLog(#"%d",sqlite3_step(statement));
}
}
sqlite3_finalize(statement);
}
sqlite3_close(database);
return NO;
}
return Yes if deleted successfully and return NO if fail to delete.