sqlite 简单使用

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////  ViewController.m//  sqlitedemo////  Created by lam_TT on 15-4-11.//  Copyright (c) 2015年 lam_TT. All rights reserved.//#import "ViewController.h"#import <sqlite3.h>@interface ViewController () {     sqlite3 *_db;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    [self openSQLite];    [self initButton];    }- (void)initButton {    NSArray *array = [[NSArray alloc]initWithObjects:@"增",@"删",@"改",@"查", nil];    for (int i = 0; i < 4; i ++) {        UIButton *button = [[UIButton alloc]init];        button.bounds = CGRectMake(0, 0, 150, 30);        button.tag = 10 + i;        [button setTitle:array[i] forState:UIControlStateNormal];        button.backgroundColor = [UIColor grayColor];        [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];        button.center = CGPointMake(CGRectGetWidth(self.view.bounds)/2, 100 + i * 50);        [self.view addSubview:button];    }}#pragma mark - 按钮点击事件- (void)buttonPressed:(UIButton *)sender {    NSInteger index = sender.tag - 10;        switch (index) {        case 0:            [self initInsertData];            break;                    case 1:            [self initDelete];            break;        case 2:            [self initUpdata];            break;        case 3:            [self initSelect];            break;    }}#pragma mark - 创建数据库- (void)openSQLite {//    sqlite3 *db;    //路径    NSString *string = [NSString stringWithFormat:@"%@/Documents",NSHomeDirectory()];    NSString *fileName = [string stringByAppendingString:@"/students.sqlite"];    //OC-C    const char *cfileName = fileName.UTF8String;        //打开数据库，没有就自动创建    int result = sqlite3_open(cfileName, &_db);        if (result == SQLITE_OK) {        NSLog(@"成功打开数据库");    }else {        NSLog(@"打开数据库失败");    }    //可用sqliteManger查看    #pragma mark - 创建表        const char  *sql="CREATE TABLE IF NOT EXISTS t_students (id integer PRIMARY KEY AUTOINCREMENT,name text NOT NULL,age integer NOT NULL);";        char *errmsg = NULL;        //参数：第一个参数为数据库的句柄（db），第二个参数为sql语句，第三个参数为回调参数，是一个指向函数的指针，如果把callback前面的*改成^则就是一个block代码段，第四个参数可以写NULL，第五个参数为错误信息，用以代码调试。    result = sqlite3_exec(_db, sql, NULL, NULL, &errmsg);        if (result == SQLITE_OK) {        NSLog(@"创建表成功");    }else {        printf("创表失败---%s----%s---%d",errmsg,__FILE__,__LINE__);    }}#pragma mark - 插入数据- (void)initInsertData {    for (int i = 0; i < 20; i ++) {        //1.拼接sql语句                NSString *name = [NSString stringWithFormat:@"数据--%d",arc4random_uniform(100)];                int age = arc4random_uniform(20) + 10;                NSString *sql=[NSString stringWithFormat:@"INSERT INTO t_students (name,age) VALUES ('%@',%d);",name,age];                //2.执行sql语句                char *errmsg = NULL;        sqlite3_exec(_db, sql.UTF8String, NULL, NULL, &errmsg);        if (errmsg) { //如果有错误信息            NSLog(@"插入数据失败-- %s",errmsg);        }else {            NSLog(@"插入数据成功");        }            }    }#pragma mark - 选择(select)查询操作- (void)initSelect {    //从这个表里面查找年龄小于20得数据    const char *sql="SELECT id,name,age FROM t_students WHERE age<20;";    sqlite3_stmt *stmt = NULL;        //进行查询前得准备工作            if (sqlite3_prepare_v2(_db, sql, -1, &stmt, NULL) == SQLITE_OK) { //SQL语句没有问题        NSLog(@"SQL语句没有问题");        //每调用一次sqlite_step函数，stmt就会指向下一条记录        while (sqlite3_step(stmt) == SQLITE_ROW) {            //取出数据            //(1)取出第0列字段得值(int类型得值)            int ID = sqlite3_column_int(stmt, 0);            //(2)取出第2列字段得值（text类型得值）            const unsigned char *name = sqlite3_column_text(stmt, 1);            //(3)取出第2列字段得值            int age = sqlite3_column_int(stmt, 2);            printf("%d %s %d\n",ID,name,age);        }                    }else {        NSLog(@"查询语句有问题，或者没有数据");    }    }#pragma mark - 删除数据- (void)initDelete {    const char *sql = "delete from t_students";    char *errmsg = NULL;    sqlite3_exec(_db, sql, NULL, NULL, &errmsg);    if (errmsg) {        NSLog(@"删除失败");    }else {        NSLog(@"删除成功");    }}- (void)initUpdata {    const char *sql = "update t_students set name = '小明' , age = 16 ;";    char *errmsg = NULL;    sqlite3_exec(_db, sql, NULL, NULL, &errmsg);    if (errmsg) {        NSLog(@"修改失败");    }else {        NSLog(@"修改成功");    }}@end
注：要导入 libsqlite3.dylib
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