iphone开发-SQLite数据库使用

我现在要使用SQLite3.0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SQLite3.0的lib库。然后包含头文件#import <sqlite3.h>

【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

 1 //创建表格，假设有五个字段，（id，cid，title，imageData ，imageLen ）
 2 //说明一下，id为表格的主键，必须有。
 3 //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。
 4 
 5 - (BOOL) createChannelsTable:(sqlite3*)db
 6 {
 7     char *sql = "CREATE TABLE channels (id integer primary key, 
 8                                         cid text, 
 9                                         title text, 
10                                         imageData BLOB, 
11                                         imageLen integer)";
12     sqlite3_stmt *statement;
13     if(sqlite3_prepare_v2(db, sql, -1, &statement, nil) != SQLITE_OK) {
14         NSLog(@"Error: failed to prepare statement:create channels table");
15         return NO;
16     }
17     int success = sqlite3_step(statement);
18     sqlite3_finalize(statement);
19     if ( success != SQLITE_DONE) {
20         NSLog(@"Error: failed to dehydrate:CREATE TABLE channels");
21         return NO;
22     }
23     NSLog(@"Create table 'channels' successed.");
24     return YES;
25 }

【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);
}