iphone/iOS开发 - SQLite数据库使用

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);
}

 

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