从SQLite的空数据库中删除

Question

I am deleting records from the database.and it is working fine .But it is crashing when there is no data in the database. The code is given Below

 int noOfRecordsDeleted;

     [self openDatabaseConnection];

    //  query = [NSString stringWithFormat:@"delete from %@ where %@",query];
    NSLog(@"del query=%@",query);
    const char *sql = [query cStringUsingEncoding:NSUTF8StringEncoding];
    sqlite3_stmt *statement = nil;

    if(sqlite3_prepare_v2(dataBaseConnection,sql, -1, &statement, NULL)!= SQLITE_OK)
    {   
                                   NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
    }



    else
    {
        int success = sqlite3_step(statement);
        NSLog(@"%d",success);
    }
    sqlite3_finalize(statement);
      noOfRecordsDeleted = sqlite3_changes(dataBaseConnection);
   [self closeDatabaseConnection];
    return noOfRecordsDeleted;

It is working fine. But if i am adding data i empty database it is crashing

[self openDatabaseConnection];

NSString *query;

query = [NSString stringWithFormat:@"insert into Userdetail(aboutMe,anniversary,areacode,birthdate,device_id,chat_id,emailid,gender   ,image,last_login,latitute,longitude,Looking_For,mobilenumber,mobilenumber1          ,mobilenumber2,mood,name,password,place,profileviews,statusmessage) values ('%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@')",aboutMe,anniversarydate,areacode,birthdate,
    device_id,chat_id,email_id,gender,image,last_login,latitude,longitude,looking_for,mobilenumber,mobilenumber1,mobilenumber2,mood,name,password,place,profileviews,statusmessage];

NSLog(@"saveNewTemplateData query=%@",query);
const char *sql = [query cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *statement = nil;if(sqlite3_prepare_v2(dataBaseConnection,sql , -1, &statement, NULL)!= SQLITE_OK)
{
    NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
}
else
{
    sqlite3_step(statement);
}
sqlite3_finalize(statement);
[self closeDatabaseConnection];

above is the code

Answer 1

First of all check the Database is empty or not by using the following statement

if(sqlite3_column_text(statement, 0) != nil){//Data exists}

Then in the if method add the code to delete the dataBase. It works fine.

Answer 2

query = [NSString stringWithFormat:@"delete from %@ where %@",query];

what does this query means I think its the mistake of your query please doublecheck it

if the error persists programmatically check by using if(sqlite3_column_text(statement, 0) != nil)

Answer 3

if (condition for check database empty (select * from table)){

}else{

//Perform Delete operation

}

Answer 4

One issue I saw that you are calling sqlite3_finalize(statement); regardless the state of sqlite3_prepare_v2 . You only need to call sqlite3_finalize if the sqlite3_prepare_v2 executed successfully.

Change that to:

if(sqlite3_prepare_v2(dataBaseConnection,sql, -1, &statement, NULL)!= SQLITE_OK)
{   
    NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
}
else
{
    int success = sqlite3_step(statement);
    NSLog(@"%d",success);
    sqlite3_finalize(statement);
}