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createChannelsTablereturn 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 = _); 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); }