iphone开发-SQLite数据库使用

lenf

　　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
　　//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 = %@",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);
}
　　就简单说这些吧。