iPhone开发SQLite数据库使用是本文要介绍的内容,我现在要使用SQLite 3.0创建一个数据库,然后在数据库中创建一个表格。首先要引入SQLite 3.0的lib库。然后包含头文件#import
1、打开数据库,如果没有,那么创建一个
- sqlite3* database_;
- -(BOOL) open
- {
- NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
- NSString *documentsDirectory = [paths objectAtIndex:0];
- NSString *path = [documentsDirectory stringByAppendingPathComponent:@"mydb.sql"];
- NSFileManager *fileManager = [NSFileManager defaultManager];
- BOOL find = [fileManager fileExistsAtPath:path];
- //找到数据库文件mydb.sql
- if (find) {
- NSLog(@"Database file have already existed.");
- if(sqlite3_open([path UTF8String], &database_) != SQLITE_OK) {
- sqlite3_close(database_);
- NSLog(@"Error: open database file.");
- return NO;
- }
- return YES;
- }
- if(sqlite3_open([path UTF8String], &database_) == SQLITE_OK) {
- bFirstCreate_ = YES;
- [self createChannelsTable:database_];//在后面实现函数createChannelsTable
- return YES;
- } else {
- sqlite3_close(database_);
- NSLog(@"Error: open database file.");
- return NO;
- }
- return NO;
- }
2、创建表格
- //创建表格,假设有五个字段,(id,cid,title,imageData ,imageLen )
- //说明一下,id为表格的主键,必须有。
- //cid,和title都是字符串,imageData是二进制数据,imageLen 是该二进制数据的长度。
- - (BOOL) createChannelsTable:(sqlite3*)db{
- char *sql = "CREATE TABLE channels (id integer primary key, \
- cid text, \
- title text, \
- imageData BLOB, \
- imageLen integer)";
- sqlite3_stmt *statement;
- if(sqlite3_prepare_v2(db, sql, -1, &statement, nil) != SQLITE_OK) {
- NSLog(@"Error: failed to prepare statement:create channels table");
- return NO;
- }
- int success = sqlite3_step(statement);
- sqlite3_finalize(statement);
- if ( success != SQLITE_DONE) {
- NSLog(@"Error: failed to dehydrate:CREATE TABLE channels");
- return NO;
- }
- NSLog(@"Create table 'channels' successed.");
- return YES;
- }
3、向表格中插入一条记录
假设channle是一个数据结构体,保存了一条记录的内容。
- - (BOOL) insertOneChannel:(Channel*)channel{
- NSData* ImageData = UIImagePNGRepresentation( channel.image_);
- NSInteger Imagelen = [ImageData length];
- sqlite3_stmt *statement;
- static char *sql = "INSERT INTO channels (cid,title,imageData,imageLen)\
- VALUES(?,?,?,?)";
- //问号的个数要和(cid,title,imageData,imageLen)里面字段的个数匹配,代表未知的值,将在下面将值和字段关联。
- int success = sqlite3_prepare_v2(database_, sql, -1, &statement, NULL);
- if (success != SQLITE_OK) {
- NSLog(@"Error: failed to insert:channels");
- return NO;
- }
- //这里的数字1,2,3,4代表第几个问号
- sqlite3_bind_text(statement, 1, [channel.id_ UTF8String], -1, SQLITE_TRANSIENT);
- sqlite3_bind_text(statement, 2, [channel.title_ UTF8String], -1, SQLITE_TRANSIENT);
- sqlite3_bind_blob(statement, 3, [ImageData bytes], Imagelen, SQLITE_TRANSIENT);
- sqlite3_bind_int(statement, 4, Imagelen);
- success = sqlite3_step(statement);
- sqlite3_finalize(statement);
- if (success == SQLITE_ERROR) {
- NSLog(@"Error: failed to insert into the database with message.");
- return NO;
- }
- NSLog(@"Insert One Channel#############:id = %@",channel.id_);
- return YES;
- }
4、数据库查询
这里获取表格中所有的记录,放到数组fChannels中。
- - (void) getChannels:(NSMutableArray*)fChannels{
- sqlite3_stmt *statement = nil;
- char *sql = "SELECT * FROM channels";
- if (sqlite3_prepare_v2(database_, sql, -1, &statement, NULL) != SQLITE_OK) {
- NSLog(@"Error: failed to prepare statement with message:get channels.");
- }
- //查询结果集中一条一条的遍历所有的记录,这里的数字对应的是列值。
- while (sqlite3_step(statement) == SQLITE_ROW) {
- char* cid = (char*)sqlite3_column_text(statement, 1);
- char* title = (char*)sqlite3_column_text(statement, 2);
- Byte* imageData = (Byte*)sqlite3_column_blob(statement, 3);
- int imageLen = sqlite3_column_int(statement, 4);
- Channel* channel = [[Channel alloc] init];
- if(cid)
- channel.id_ = [NSString stringWithUTF8String:cid];
- if(title)
- channel.title_ = [NSString stringWithUTF8String:title];
- if(imageData){
- UIImage* image = [UIImage imageWithData:[NSData dataWithBytes:imageData length:imageLen]];
- channel.image_ = image;
- }
- [fChannels addObject:channel];
- [channel release];
- }
- sqlite3_finalize(statement);
- }
小结:iPhone开发SQLite数据库使用的内容介绍完了,希望本文对你有所帮助。