iphone开发-SQLite数据库使用

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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;
}

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//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;
}

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- (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](mailto:%@%22,channel.id)_);
    return YES;
}

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- (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);
}

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// 首先获取iPhone上Sqlite3的数据库文件的地址  
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
NSString *documentsDirectory = [paths objectAtIndex:0];  
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"database_name"];  
// 打开Sqlite3的数据库文件  
sqlite3 *database;  
sqlite3_open([path UTF8String], &database);  
// 定义SQL文  
sqlite3_stmt *stmt;  
const char *sql = "SELECT * FROM table_name WHERE pk=? and name=?";  
sqlite3_prepare_v2(database, sql, -1, &stmt, NULL);  
// 邦定第一个int参数  
sqlite3_bind_int(stmt, 1, 1);  
// 邦定第二个字符串参数  
sqlite3_bind_text(stmt, 2, [title UTF8String], -1, SQLITE_TRANSIENT);  
// 执行SQL文，并获取结果  
sqlite3_step(stmt);  
// 释放资源  
sqlite3_finalize(stmt);  
// 关闭Sqlite3数据库  
sqlite3_close(database);