iPhone中的SQLite使用_SQL

iPhone中的SQLite应用

From :http://linglong117.blog.163.com/blog/static/277145472009111403520676/

SQLite是基于C的API，在iPhone中的运行速度超级快（在苹果网站上也有一个对比，确实应该是速度最快的）。

由于在iPhone3.0上已经支持了Core Data，是苹果一个新的API，并且是基于SQlite的。速度也是非常快吧，信不信由你。所以我们对SQLite仅需要懂一些即可，以下是一些基础信息

//============

首先在FrameWorks ?中加入SQLite 的库: ?lib/libsqlite3.dylib?

完整路径如下：

/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.0.sdk/usr/lib/libsqlite3.dylib

?然后包含头文件#import <sqlite3.h>

一般操作：

//=============

//databasePath 数据库路径

//database 数据库名

int n = sqlite3_open([databasePath UTF8String], &database); ? //打开数据库

if(n != SQLITE_OK){ //判断数据库是否打开

NSLog(@"can not open the database");

return;

}

?? ? ?//执行sql 语句

sqlite3_stmt *stmt;

char *sql = "SELECT TimeDesc FROM tblTime WHERE isActivated=1"; ?//sql 语句

sqlite3_prepare_v2(database, sql, -1, &stmt, NULL);

int code = sqlite3_step(stmt);

NSMutableArray *arrayData = [[NSMutableArray alloc] init];

NSMutableDictionary *dicTimeDesc ?= [[NSMutableDictionary alloc] init];

?? ? //把sql 语句的查询结果存储到 NSMutableArray 中

while (code == SQLITE_ROW) {

char *c;

NSString *s;

c = (char *)sqlite3_column_text(stmt, 0);

s = [NSString stringWithUTF8String:c];

[dicTimeDesc setObject:s forKey:@"TimeDesc"];

[s release];

?? ? ? ? ? ? ? ?//int n;

//n = sqlite3_column_int(stmt2,0);

[arrayData addObject:dicTimeDesc];

code = sqlite3_step(stmt);

}

sqlite3_finalize(stmt);?

sqlite3_close(database); ?//关闭数据库

?? ? ?//带参数的sql 语句

??sqlite3_stmt *stmt;

char *sql = "SELECT SNo,BrandName,PicFileName,FolderGUID,PicDesc,PicDescLocation,IconSpecName,StyleName,PicFileName_H FROM tblProduct where BrandName = ? order by SNo";

sqlite3_prepare_v2(database, sql, -1, &stmt, NULL);

sqlite3_bind_text(stmt, 1, [brandName UTF8String], -1, SQLITE_TRANSIENT);

NSMutableDictionary *d;

char *c;

NSString *s;

int code = sqlite3_step(stmt);

while (code == SQLITE_ROW) {

//sql 语句检索结果

}

//=========

//执行事务

@try {

sqlite3_exec(database,"BEGIN TRANSACTION",0,0,0); ?//事务开始

NSString *s = [[NSString alloc] initWithUTF8String:[要执行的sql 语句 ?UTF8String]];

char *sql = (char *) [s UTF8String];

int r = sqlite3_exec( database, sql , 0, 0, 0 );

if(r != SQLITE_OK){

//NSLog(@" sql: %@" ,s);

//NSLog(@"r = %d",r);

}

NSLog(@"updateSql %@",ssql);

NSLog(@"r = %d",r);

[s release];

}

@catch (NSException * em) {

NSLog(@"failed to read %@",[em description]);

}

@finally {

//NSLog(@"failed to read %@",[e description]);

}

int?result = sqlite3_exec(database,"COMMIT",0,0,&error); //COMMIT

?? ??

//==============

//以下内容为网络上摘取的，我没经过验证，可以做为参考

【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);
}

//===================

打开数据库

sqlite3 *database = NULL; //建立一个sqlite数据库变量  ?  int sqlite3_open(const char *文件名, sqlite3 **db); //那个文件名需要是cString，                                                     //之后那个db对象使用我们建立的database变量  ?  //以下是一个开打的例子：  NSString *fileAddress = [[NSBundle mainBundle] pathForResource:@"预存文件的文件名" ofType:@"db"]; //db是扩展名  ?  if(sqlite3_open([fileAddress UTF8String], &amp;database) == SQLITE_OK) //UTF8String方法转换NSString为cString

执行一个SQLite语句：

int sqlite3_exec(sqlite3 *db, const char *sql, int (*callback)(void*,int,char**,char**), void *context, char **error);

关闭一个数据库：

int sqlite3_close(sqlite3 *db); //这个不用解释了吧

一个响应函数的格式：

int callback(void *context, int count, char **values, char **columns);  ?