How to update an entry in sqlite3? - ios

Question

Im super new to ios (Objective-C) and sql and Im following a tutorial of sqlite (specifically sqlite3) found here: http://www.tutorialspoint.com/ios/ios_sqlite_database.htm
and i implemented everything correctly. The problem is that if I try to enter information with the same reg id (The primary key which is used to find elements in the database), it complains about the key not being unique.
- (BOOL) saveData:(NSString*)registerNumber name:(NSString*)name
department:(NSString*)department year:(NSString*)year;
{
const char *dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath, &database) == SQLITE_OK)
{
NSString *insertSQL =
[NSString stringWithFormat:#"insert into studentsDetail (regno,name, department, year) values (\"%d\",\"%#\", \"%#\", \"%#\")",[registerNumber integerValue], name, department, year];
const char *insert_stmt = [insertSQL UTF8String];
sqlite3_prepare_v2(database, insert_stmt,-1, &statement, NULL);
int s = sqlite3_step(statement);
const char *errmsg = sqlite3_errmsg(database);
if (s == SQLITE_DONE)
{
sqlite3_reset(statement);
return YES;
}
else {
sqlite3_reset(statement);
return NO;
}
}
return NO;
}
How do I go about making the saveData: action actually update the entry inside the database instead of just being rejected?
Thanks!

Answer 1

"I want to extend it so that if I try to enter an existing reg id, it
will overwrite the remaining properties with the new ones"
If this is what you are trying to accomplish then you should not be using an INSERT statement. The purpose of the primary key is to protect the database from duplicate rows with the same primary key. When you look at it that way, the rejection is appropriate.
What you really want is to use INSERT OR REPLACE
If you're a beginner to both sql and objective c, I'd recommend a sqlite wrapper I created that is aimed at beginners: TankDB
Edit:
Code example:
INSERT OR REPLACE INTO studentsDetail (regno,name, department, year) values (\"%d\",\"%#\", \"%#\", \"%#\")"
Refer to this question to make sure that you don't actually mean to use 'UPSERT'. Beware that INSERT OR REPLACE does not update the existing row with the new information. It will completely delete the existing row and replace it.
Edit2: Open, prepare, step, finalize, close
const char *dbpath = [_databasePath UTF8String];
if(sqlite3_open(dbpath, &_database) == SQLITE_OK) {
const char *command = [query UTF8String];
// Perform the query
if (sqlite3_prepare_v2(_database, command, -1, &selectstmt, NULL) == SQLITE_OK) {
// For each row returned
while (sqlite3_step(selectstmt) == SQLITE_ROW) {
// Do stuff
}
}
sqlite3_finalize(selectstmt);
}
sqlite3_close (_database);