what does if exist return - ios

Question

I am using sqlite3 as my database for ios project and would like to execute if exist statement to see whether the object exists and if does, update or else insert.
I am using this function to query the database
-(void)updateStatus:(NSString *)queryString {
NSString *docsDir;
NSArray *dirPaths;
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
m_singleton = [Singleton sharedSingleton];
strDatabasePath = [NSString stringWithString:[docsDir stringByAppendingPathComponent:#"BorneoMotors.db"]];
NSFileManager *filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath: strDatabasePath] == YES)
{
const char *dbpath = [strDatabasePath UTF8String];
if (sqlite3_open(dbpath, &sqlDatabase) == SQLITE_OK)
{
const char* beginString = "BEGIN;";
sqlite3_stmt *compiledstatement;
sqlite3_prepare_v2(sqlDatabase, beginString, -1, &compiledstatement, NULL);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else NSLog(#"Failed!");
sqlite3_finalize(compiledstatement);
NSLog(#"QUERY : %#",queryString);
const char *selectStatement = [queryString UTF8String];
sqlite3_prepare_v2(sqlDatabase, selectStatement, -1, &compiledstatement, NULL);
//sqlite3_bind_text(compiledstatement,1,[statusString UTF8String],-1,SQLITE_TRANSIENT);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else NSLog(#"Failed!");
sqlite3_finalize(compiledstatement);
const char* endString="END;";
sqlite3_prepare_v2(sqlDatabase, endString, -1, &compiledstatement, NULL);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else NSLog(#"Failed!");
sqlite3_finalize(compiledstatement);
sqlite3_close(sqlDatabase);
}
else NSLog(#"Failed to open table");
}
}
The problem i have is that what this if exists will return and how do i move upon that.
NSString *checkstring = [NSString stringWithFormat:#"IF EXISTS (SELECT * FROM DATABASE WHERE id = %#",cars.ID];
DB *accessdb = [[DB alloc] init];
[accessdb updateStatus:checkstring];
if (??){
NSString *queryString = [NSString stringWithFormat: #"UPDATE DATABASE SET STATUS='%#' WHERE \"DATABASEID\" = '%#'", cars.status,cars.ID];
const char *selectStatement = [queryString UTF8String];
sqlite3_prepare_v2(sqlDatabase, selectStatement, -1, &statement, NULL);
//sqlite3_bind_text(compiledstatement,1,[statusString UTF8String],-1,SQLITE_TRANSIENT);
if (sqlite3_step(statement) == SQLITE_DONE) {}
else NSLog(#"Failed!");
sqlite3_finalize(statement);
}else{
insert}
How do i check whether the existence of the object? What does the if exists return? Need some guidance...

Answer 1

SQLite does not have an IF statement.
To check whether some record exist, just execute a query like
SELECT 1 FROM database WHERE ID = ?
and test in your app whether or not you get back a record.
For your update/insert problem: If you have a unique index on the key colum, you could use the INSERT OR REPLACE command which automatically deletes the old record if the new one would create a duplicate.