SqlLite 基本操作

• ●  实际上SQLite是?无类型的

• ●  就算声明为integer类型,还是能存储字符串?文本(主键除外)

• ●  建表时声明啥类型或者不声明类型都可以,也就意味着创表语句可以这么写:

          • create table t_student(name, age); 

#import "ViewController.h"

#import <sqlite3.h>

@interface ViewController ()

//1.创建数据库 (保存路径)

@property (nonatomic,assign)sqlite3 *db;

@end

@implementation ViewController

- (IBAction)insertData:(UIButton *)sender {

    //3.增加 数据 (100条 数据随机)

    for (int i = 0; i <2; i++) {

        NSString *strName = [NSString stringWithFormat:@"8mingyeuxin-%d",i];

        NSString *sqlStr = [NSString stringWithFormat:@"INSERT INTO t_student (name ,score)VALUES(‘%@‘,%.02f)",strName,arc4random_uniform(1000)/10.0];

        //执行

       int success =   sqlite3_exec(_db, sqlStr.UTF8String, NULL, NULL, NULL);

        if (success == SQLITE_OK) {

            NSLog(@"添加成功!");

        }else{

            NSLog(@"添加失败!");

        }

    }

}

- (IBAction)deleteData:(UIButton *)sender {

    //4.删除 数据 (70 - 80 分数)

    NSString *sqlStr = @"DELETE FROM t_student WHERE score > 80.0";

    //执行

    int success =   sqlite3_exec(_db, sqlStr.UTF8String, NULL, NULL, NULL);

    if (success == SQLITE_OK) {

        NSLog(@"删除成功!");

    }else{

        NSLog(@"删除失败!");

    }

}

- (IBAction)updateData:(UIButton *)sender {

    //5.修改 数据 (修改分数小于60.0为60.0)

    NSString *sqlStr = @"UPDATE t_student SET score = 60.0 WHERE score < 60.0";

    //执行

    int success = sqlite3_exec(_db, sqlStr.UTF8String, NULL, NULL, NULL);

    if (success == SQLITE_OK) {

        NSLog(@"修改成功!");

    }else{

        NSLog(@"修改失败!");

    }

}

- (IBAction)selectData:(UIButton *)sender {

    //6.查询数据 ( score >= 60)

    //NSString *sqlStr = @"SELECT * FROM t_student WHERE score > 60.0 ORDER BY score DESC;";

    //查询数据 ( name  中带 8 数字)

    NSString *sqlStr = @"SELECT * FROM t_student WHERE name LIKE ‘%ming%‘";

    //查询之后  把结果放在 stmt对象

    // 保存所有的结果集

    sqlite3_stmt *stmt = nil;

    sqlite3_prepare_v2(_db, sqlStr.UTF8String, -1, &stmt, NULL);

    //获取到所有结果  每一步  查询到一条记录

    while (sqlite3_step(stmt) == SQLITE_ROW) {

        //取出一条记录

        // name TEXT    column

        const unsigned char * name =  sqlite3_column_text(stmt, 1);

        NSString *strName = [NSString stringWithCString:(const char *)name encoding:NSUTF8StringEncoding];

        //score  REAL

        double score =  sqlite3_column_double(stmt, 2);

        NSLog(@"name = %@  score = %f",strName,score);

    }

}

- (void)viewDidLoad {

    [super viewDidLoad];

    //打开数据库 如果没有就创建

    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject]stringByAppendingPathComponent:@"data.sqlite"];

    NSLog(@"%@",path);

    int success =  sqlite3_open(path.UTF8String, &_db);

    if (success == SQLITE_OK) {

        NSLog(@"创建数据库成功!");

        //2.创建表 (指定字段  -> 需求: 保存 学生信息 id  name score)

        //用sql语句 来创建

        //编写sql语句

        NSString *str = @"CREATE TABLE IF NOT EXISTS t_student (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, score REAL NOT NULL)";

        //执行sql语句

        int success_t =  sqlite3_exec(_db, str.UTF8String, NULL, NULL, NULL);

        if (success_t == SQLITE_OK) {

            NSLog(@"创建表成功!");

        }else{

            NSLog(@"创建表失败!");

        }

    }else{

        NSLog(@"创建数据库失败!");

    }

    //关闭数据库

    sqlite3_close(_db);

}

@end