iphone開發-SQLite資料庫使用

轉自：http://yuxiang13115204.blog.163.com/blog/static/26802022200921410845642/

我現在要使用SQLite3.0建立一個資料庫，然後在資料庫中建立一個表格。

首先要引入SQLite3.0的lib庫。然後包含標頭檔#import <sqlite3.h>

【1】開啟資料庫，如果沒有，那麼建立一個

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];

    //找到資料庫檔案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_];//在後面實現函數createChannelsTable

        return YES;
    } else {
        sqlite3_close(database_);
        NSLog(@"Error: open database file.");
        return NO;
    }
    return NO;
}

【2】建立表格

//建立表格，假設有五個欄位，（id，cid，title，imageData ，imageLen ）

//說明一下，id為表格的主鍵，必須有。

//cid，和title都是字串，imageData是位元據，imageLen 是該位元據的長度。
- (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】向表格中插入一條記錄

假設channle是一個資料結構體，儲存了一條記錄的內容。

- (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(?,?,?,?)";

    //問號的個數要和(cid,title,imageData,imageLen)裡面欄位的個數匹配，代表未知的值，將在下面將值和欄位關聯。
    int success = sqlite3_prepare_v2(database_, sql, -1, &statement, NULL);
    if (success != SQLITE_OK) {
        NSLog(@"Error: failed to insert:channels");
        return NO;
    }
   

   //這裡的數字1，2，3，4代表第幾個問號
    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】資料庫查詢

這裡擷取表格中所有的記錄，放到數組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.");
    }
    //查詢結果集中一條一條的遍曆所有的記錄，這裡的數字對應的是列值。
    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);
}

 

就簡單說這些吧。