快速掌握SQLite数据库在iOS开发中的应用

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我此刻要应用SQLite3.0创建一个数据库，然后在数据库中创建一个表格。

起首要引入SQLite3.0的lib库。然后包含头文件#import

【1】翻开数据库，假定没有，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_];//在前面完成函数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，假定有五个字段，（id，cid，title，imageData ，imageLen ）

//诠释一下，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】向表格中拔出一笔记录

假定channle是一个数据布局体，保管了一笔记录的内容。

- (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)外面字段的个数婚配，代表未知的值，将不才面将值和字段关联。

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

这里获得表格中一切的记录，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一切的记录，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);

}

就简单说这些吧