Fetching data and compering in iphone

Can any one help me .How can a fetch the remote data using WEB API's or SERVER API's with of JSON & then store into SQLite table in iphone how can do this .For fetching data I want to use JSON.In SQLite database table is user_detailes which ha开发者_运维技巧s username & password .And the server also has the same data which i want fetch. Help me to this.

Give some hints or links or sample to solve this

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NSString * txtUsername = @"";

NSString * txtPassword = @"";

sqlite3 *database;

NSString *sqlStatement = @"";

if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) 
{

    sqlStatement = [NSString stringWithString:@"select * from account_info "];
    NSLog(@"%@",sqlStatement);
    sqlite3_stmt *compiledStatement;

    if(sqlite3_prepare_v2(database, [sqlStatement cStringUsingEncoding:NSUTF8StringEncoding], -1, &compiledStatement, NULL) == SQLITE_OK) 
    {

        while(sqlite3_step(compiledStatement) == SQLITE_ROW) 
        {
            txtUsername = [[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)] retain];
            txtPassword = [[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)] retain];

        }
    }

    sqlite3_finalize(compiledStatement);
    sqlite3_close(database);

if(txtUsername isEqulaToString:@"user1"]) { //use UIAlertView here }