首先，添加framework：libsqlite3.0.dylib需要在对应文件的头文件中加入：#import "/usr/include/sqlite3.h"
并在Frameworks中加入所需的库，否则会报错：Undefined symbols: "_sqlite3_open", referenced from:
加入库的方法是：image
选择sqlite库：image
选择完的效果：image
下面是代码：//sqlite    [self openDataBase];   //[self createTable];   //[self insertTable];   [self queryTable];   [self deleteTable];   [self queryTable];
实现：//open database
- (void)openDataBase
{   NSArray *documentsPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory   , NSUserDomainMask    , YES);    NSString *databaseFilePath=[[documentsPaths objectAtIndex:0] stringByAppendingPathComponent:@"db.sql"];   if (sqlite3_open([databaseFilePath UTF8String], &database)==SQLITE_OK)    {    NSLog(@"open sqlite db ok.");    }   else    {   NSLog( @"can not open sqlite db " );   //close database   sqlite3_close(database);    }
}   //create table
- (void)createTable
{   char *errorMsg;   const char *createSql="create table if not exists persons (id integer primary key autoincrement,name text)";   if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK)    {    NSLog(@"create ok.");    }   else    {   NSLog( @"can not create table" );   [self ErrorReport:(NSString *)createSql];   }
}   //insert table
- (void)insertTable
{   char *errorMsg;   const char *insertSql="insert into persons (name) values ('田周辉')";    if (sqlite3_exec(database, insertSql, NULL, NULL, &errorMsg)==SQLITE_OK)    {    NSLog(@"insert ok.");    }   else    {   NSLog( @"can not insert it to table" );   [self ErrorReport: (NSString *)insertSql];   }
}   //error
- (void)ErrorReport: (NSString *)item
{   char *errorMsg;   if (sqlite3_exec(database, (const char *)item, NULL, NULL, &errorMsg)==SQLITE_OK)   {    NSLog(@"%@ ok.",item);    }   else    {    NSLog(@"error: %s",errorMsg);    sqlite3_free(errorMsg);    }
}   //query table
- (void)queryTable
{   const char *selectSql="select id,name from persons";    sqlite3_stmt *statement;    if (sqlite3_prepare_v2(database, selectSql, -1, &statement, nil)==SQLITE_OK)   {    NSLog(@"select ok.");    while (sqlite3_step(statement)==SQLITE_ROW)//SQLITE_OK SQLITE_ROW   {    int _id=sqlite3_column_int(statement, 0);    NSString *name=[[NSString alloc] initWithCString:(char *)sqlite3_column_text(statement, 1) encoding:NSUTF8StringEncoding];    NSLog(@"row>>id %i, name>> %@",_id,name);    }   }   else    {   //error   [self ErrorReport: (NSString *)selectSql];   }   sqlite3_finalize(statement);
}   //delete table
- (void)deleteTable
{      char *errorMsg;   [self openDataBase];   const char *sql = "DELETE FROM persons where id=24";   if (sqlite3_exec(database, sql, NULL, NULL, &errorMsg)==SQLITE_OK)    {    NSLog(@"delete ok.");    }   else    {   NSLog( @"can not delete it" );   [self ErrorReport: (NSString *)sql];   }   }
命令行：sqlite3 database  //创建数据库 crate table tableFile(id smallint, file_name varchar(256), up_state smallint, file_size smallint); //创建一个表格 insert into tableFile values(1, "200110101.rcu", 100, 4500);   //插入数据
5 如何访问SQLite3数据库
sqlite3_open //打开数据库
sqlite3_prepare //将UTF－8格式的SQL语句转换为指向已备语句的指针
sqlite3_column_string //返回某一行的字符串
sqlite3_finalize //删除一条已备语句
sqlite3_close //关闭数据库 6 source code - (id)lookupSingularSQL:(NSString *)sql forType:(NSString *)rettype { sqlite3_stmt *statement; id result; if (statement = [self prepare:sql]) { if (sqlite3_step(statement) == SQLITE_ROW) { if ([rettype compare:@"text"] == NSOrderedSame) { char temp_buf[256]; memset(temp_buf, 0, 256); sprintf(temp_buf, "%s %s %s %s",  (char *)sqlite3_column_text(statement,0), (char *)sqlite3_column_text(statement,1), (char *)sqlite3_column_text(statement,2), (char *)sqlite3_column_text(statement,3) ); result = [NSString stringWithUTF8String:temp_buf]; //result = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement,0)]; } else if ([rettype compare:@"integer"] == NSOrderedSame) { result = (id)sqlite3_column_int(statement,0); } } } sqlite3_finalize(statement); return result; }
应该有个成员变量，比如我的代码：@interface DetailViewController : UIViewController {
UIPopoverController *popoverController;
UIToolbar *toolbar;
id detailItem;
UILabel *detailDescriptionLabel;
sqlite3 *database;
打开数据库SQLite数据库是文件数据库，是保存在文件系统中的。因此需要知道文件保存到哪里，可参见iOS中对文件的操作。比如本文保存到Documents目录下。代码：NSArray *documentsPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory
, NSUserDomainMask
, YES);
NSString *databaseFilePath=[[documentsPaths objectAtIndex:0] stringByAppendingPathComponent:@"mydb"];
if (sqlite3_open([databaseFilePath UTF8String], &database)==SQLITE_OK) {
NSLog(@"open sqlite db ok.");
}
通过ssh查看Documents目录，发现mydb文件已经创建。sqlite的策略是如果有该文件就打开，如果没有就创建文件，也就是创建数据库。这里要注意，使用的是C语法，sqlite3_open传入的是database的地址。关闭数据库数据库使用完毕后，要关闭，比如退出应用的时候：- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
sqlite3_close(database);
self.popoverController = nil;
}
建表语句数据库打开以后，如果没有表，建表：char *errorMsg;
const char *createSql="create table if not exists persons (id integer primary key autoincrement,name text)";
if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK) {
NSLog(@"create ok.");
}
这里要特别注意errorMsg传的是地址，因为该函数要通过地址引用来写报错字符信息。向表中插入记录和建表语句类似：const char *insertSql="insert into persons (name) values(‘张三’)";
if (sqlite3_exec(database, insertSql, NULL, NULL, &errorMsg)==SQLITE_OK) {
NSLog(@"insert ok.");
}
错误信息的处理如果在多个地方使用errorMsg，那么每次使用完毕要清空一下字串，比如这样：if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK) {
NSLog(@"create ok.");
}else {
NSLog(@"error: %s",errorMsg);
sqlite3_free(errorMsg);
}
查询结果集结果集的查询，需要用到statement：const char *selectSql="select id,name from persons";
sqlite3_stmt *statement;
if (sqlite3_prepare_v2(database, selectSql, -1, &statement, nil)==SQLITE_OK) {
NSLog(@"select ok.");
}
while (sqlite3_step(statement)==SQLITE_ROW) {
int _id=sqlite3_column_int(statement, 0);
char *name=(char *)sqlite3_column_text(statement, 1);
NSLog(@"row>>id %i, name %s",_id,name);
}
sqlite3_finalize(statement);
不过这里有个问题，看看打印的日志：image
乱码。因为直接用的char类型来做的。解决办法是，用nsstring替代char：while (sqlite3_step(statement)==SQLITE_ROW) {
int _id=sqlite3_column_int(statement, 0);
NSString *name=[[NSString alloc] initWithCString:(char *)sqlite3_column_text(statement, 1) encoding:NSUTF8StringEncoding];
NSLog(@"row>>id %i, name %@",_id,name);
}
char生成nsstring的时候做一次显式的编码。问题解决：image
这说明：写入数据库，用char的方式没有问题，写入数据库的编码是对的;从库中取出，可能默认使用ascii解码，造成显示乱码。使用sqlite c api，要经常参考官方函数文档：http://www.sqlite.org/c3ref/funclist.html