SQLite是一个开源的嵌入式关系数据库，它在2000年由D. Richard Hipp发布，它的减少应用程序管理数据的开销，SQLite可移植性好，很容易使用，很小，高效而且可靠。
SQLite嵌入到使用它的应用程序中，它们共用相同的进程空间，而不是单独的一个进程。从外部看，它并不像一个RDBMS，但在进程内部，它却是完整的，自包含的数据库引擎。
嵌入式数据库的一大好处就是在你的程序内部不需要网络配置，也不需要管理。因为客户端和服务器在同一进程空间运行。SQLite 的数据库权限只依赖于文件系统，没有用户帐户的概念。SQLite 有数据库级锁定，没有网络服务器。它需要的内存，其它开销很小，适合用于嵌入式设备。你需要做的仅仅是把它正确的编译到你的程序。
ios下使用sqlite首先导入SQLite3.0的lib库。然后包含头文件#import <sqlite3.h>
下面的代码主要对常用的数据库操作如查询、插入、删除、更新等进行封装，方便以后使用。
头文件代码如下：
#import <Foundation/Foundation.h> #import <sqlite3.h> #import "User.h" #define kFileName @"database.sqlite" @interface SQLite3Util : NSObject{ sqlite3_stmt *stmt; sqlite3 *database; } - (NSString *)dataFilePath; - (int)getCountOfDB; - (BOOL)insertOrUpdateUser:(NSString *)sql; - (BOOL)deleteUser:(NSInteger)userId; - (NSMutableArray *)getUsers; - (User *)getUser:(NSInteger)userId; - (BOOL)openDatabase; - (void)closeDatabase; @end实现如下：
#import "SQLite3Util.h" @implementation SQLite3Util //Return Database path - (NSString *)dataFilePath{ NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUSErDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kFileName]; } //Insert or update data - (BOOL)insertOrUpdateUser:(NSString *)sql{ if ([self openDatabase]) { if (sqlite3_exec(database, [sql UTF8String], nil, &stmt, nil) != SQLITE_OK) { NSLog(@"Insert or update is failed!"); return NO; }else{ // sqlite3_finalize(stmt); NSLog(@"Insert or update successfully!"); return YES; } sqlite3_close(database); } return NO; } //Delete a user from database - (BOOL)deleteQuestion:(NSInteger)userId{ NSString *sql = [NSString stringWithFormat:@"Delete FROM User WHERE id = %i", userId]; if ([self openDatabase]) { if (sqlite3_exec(database, [sql UTF8String], nil, &stmt, nil) != SQLITE_OK) { NSLog(@"Delete data is failed!"); return NO; }else{ sqlite3_finalize(stmt); NSLog(@"Delete data successfully!"); return YES; } sqlite3_close(database); } return NO; } //Get users - (NSMutableArray *)getUsers{ NSMutableArray *users = [[NSMutableArray alloc] init]; NSString *sql = [NSString stringWithFormat:@"SELECT * FROM User]; if ([self openDatabase]) { if (sqlite3_prepare_v2(database, [sql UTF8String], -1, &stmt, nil) == SQLITE_OK) { // NSLog(@"SQL is Prepared!"); while (sqlite3_step(stmt) == SQLITE_ROW) { User *user = [[Question alloc] init]; char *name = (char *)sqlite3_column_text(stmt, 0); [user setName:[NSString stringWithUTF8String:name]]; char *index = (char *)sqlite3_column_text(stmt, 1); [user setId:[[NSString stringWithUTF8String:index] intValue]]; [users addObject: user]; } sqlite3_finalize(stmt); } } sqlite3_close(database); return users; } //Get count of the users - (int)getCountOfDB{ int count = 0; NSString *sql = [NSString stringWithFormat:@"SELECT * FROM User"]; if ([self openDatabase]) { if (sqlite3_prepare_v2(database, [sql UTF8String], -1, &stmt, nil) == SQLITE_OK) { while (sqlite3_step(stmt) == SQLITE_ROW) { count ++; } sqlite3_finalize(stmt); } } return count; } - (User *)getUser:(NSInteger)userId{ User *user = [[User alloc] init]; NSString *sql = [NSString stringWithFormat:@"SELECT * FROM User WHERE id = %i", userId]; // NSLog(@"sql = %@", sql); if ([self openDatabase]) { if (sqlite3_prepare_v2(database, [sql UTF8String], -1, &stmt, nil) == SQLITE_OK) { NSLog(@"SQL is Prepared!"); while (sqlite3_step(stmt) == SQLITE_ROW) { char *name = (char *)sqlite3_column_text(stmt, 0); [user setName:[NSString stringWithUTF8String:name]]; [user setId:userId]; } sqlite3_finalize(stmt); } } return user; } - (BOOL)openDatabase{ if (sqlite3_open([[self dataFilePath] UTF8String], &database) == SQLITE_OK) { NSLog(@"SQL is Open!"); return YES; } return NO; } - (void)closeDatabase{ sqlite3_close(database); } @end
在以后的代码中直接调用即可，如查询一个用户：