数据库之SQLite增删改查

一个demo测试Sqlite的增删改查

- (void) createDatabase {
    NSString *dbName = @"/Users/chance/Desktop/userinfo.db";
    // ios数据库要包含2个
    // #import <sqlite3.h>
    // libsqlite3.dylib
    // 1. 打开数据库
    sqlite3 *dbPointer = NULL;
    int ret = sqlite3_open(
            [dbName UTF8String], &dbPointer);
    // 打开数据dbName 如果这个数据不存在就创建，如果存在就直接打开

    if (ret != SQLITE_OK) {
        NSLog(@"打开数据库失败");
    }
    // 2. 创建一张表
    // 创建和 创建表 插入记录 删除记录 修改记录操作一模一样
    // 只有查询记录不一样
    NSString *sql = @"create table if not exists userinfo (ID int, Name varchar(64), Age int, City varchar(64)); ";

    char *errMsg = NULL;
    ret = sqlite3_exec(dbPointer, [sql UTF8String], NULL, NULL, &errMsg);
    // 如果执行sql语句错误了 把错误的字符串errMsg字符串中

    if (ret != SQLITE_OK) {
        NSLog(@"sql语句有错误 errMsg is %s", errMsg);
        sqlite3_free(errMsg);
    }
    // 3. 加入一条记录

    NSString *insertSQL = @"insert into userinfo (ID, Name, Age, City) values ('10024', '张三', '88', '北京');";
    ret = sqlite3_exec(dbPointer, [insertSQL UTF8String], NULL, NULL, NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"插入记录错误");
    }
    // 4.再加几条
    insertSQL = @"insert into userinfo (ID, Name, Age, City) values ('10025', '李四', '19', '上海');";
    ret = sqlite3_exec(dbPointer, [insertSQL UTF8String], NULL, NULL, NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"插入记录错误");
    }

    insertSQL = @"insert into userinfo (ID, Name, Age, City) values ('10027', '李胡', '21', '武汉');";
    ret = sqlite3_exec(dbPointer, [insertSQL UTF8String], NULL, NULL, NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"插入记录错误");
    }
    insertSQL = @"insert into userinfo (ID, Name, Age, City) values ('10099', '赵美双', '28', '郑州');";
    ret = sqlite3_exec(dbPointer, [insertSQL UTF8String], NULL, NULL, NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"插入记录错误");
    }


    // 4. 修改一条记录


        sqlite3_stmt *statement;//这相当一个容器，放转化OK的sql语句
        //组织SQL语句
       char *updateSQL = "update userinfo set Name = '李春桂' WHERE ID = '10099' ";

        //将SQL语句放入sqlite3_stmt中
        int success = sqlite3_prepare_v2(dbPointer, updateSQL, -1, &statement, NULL);
        if (success != SQLITE_OK) {
            NSLog(@"Error: failed to update:testTable");
        }


    //执行SQL语句。这里是更新数据库
    success = sqlite3_step(statement);
    //释放statement
    sqlite3_finalize(statement);

// //如果执行失败
// if (success == SQLITE_ERROR) {
// NSLog(@"Error: failed to update the database with message.");
// }
// 

    // 5. 查询所有的记录
    NSString *selectSQL = @"select ID, Name, Age, City from userinfo;";
    sqlite3_stmt *result = NULL;
    sqlite3_prepare_v2(dbPointer, [selectSQL UTF8String], -1, &result, NULL);
    // 去数据库dbPointer中做selectSQL查询语句 然后返回值放在result中
    // result游标在-1
    int row = 0;
    while (1) {
        ret = sqlite3_step(result);
        // 在result游标往下走一步，
        if (ret == SQLITE_ROW) {
            // 这一行确实有数据
            // 读取当前行的0, 1, 2, 3
            int ID = sqlite3_column_int(result, 0);
            const unsigned char *cname = sqlite3_column_text(result, 1);
            NSString *name = [NSString stringWithUTF8String:
                        (const char *)cname];
            int age = sqlite3_column_int(result, 2);
            const unsigned char *ccity = sqlite3_column_text(result, 3);
            NSString *city = [NSString stringWithUTF8String:(const char *)ccity];
            NSLog(@"第%d行 ID %d name %@ age %d city %@", 
                  row, ID, name, age, city);

            row++;
        } else {
            break;
        }
    }
    // 释放结果 释放内存
    sqlite3_finalize(result);

    // 6. 要获取数据库userinfo表一共有多少行
    NSString *sqlCount = @"select count(*) from userinfo;";
    sqlite3_stmt *countResult = NULL;
    sqlite3_prepare_v2(dbPointer, [sqlCount UTF8String], -1, &countResult, NULL);
    sqlite3_step(countResult); //走一步
    int count = sqlite3_column_int(countResult, 0);
    NSLog(@"数据库userinfo表一共 %d", count);
    sqlite3_finalize(countResult);

    //删除
    NSString *deleteSQL = @"delete from userinfo where id ='10025'"; //删除userid为4的表
    if (sqlite3_exec(dbPointer, [deleteSQL UTF8String], NULL, NULL, &errMsg) == SQLITE_OK) {
        printf("delete ok.\n");
    }
    else {
        printf("can't delete it\n");
    }


    // 4. 关闭数据库
    sqlite3_close(dbPointer);
}

同样的例子用FMDB做

- (void) createDatabaseFMDB {
    NSString *dbName = @"/Library/WebServer/Documents/1206/8-16/userinfo.db";
    FMDatabase *database = [FMDatabase databaseWithPath:dbName];

    if (![database open]) {
        NSLog(@"open database error");
    }
    NSString *sql = @"create table if not exists userinfo (ID integer primary key autoincrement, Name varchar(64), Age int, City varchar(64)); ";
    [database executeUpdate:sql];

    NSString *insertSQL = @"insert into userinfo (Name, Age, City) values ('张三', '22', '北京');";
    [database executeUpdate:insertSQL];

    [database executeUpdate:@"insert into userinfo (Name, Age, City) values (?, ?, ?);",
            @"fmdb", @"34", @"北京"];

    [database executeUpdate:@"UPDATE User SET Name = ? WHERE ID = ? ",@"修改名字", @"1"]; [database executeUpdate:@"DELETE FROM userinfo WHERE ID = ?", @"2"]; // 查询 NSString *firstRecord = [database stringForQuery:@"SELECT Name FROM userinfo WHERE ID = ?", @"1"]; NSLog(@"first record is %@", firstRecord); FMResultSet *rs = [database executeQuery:@"SELECT * FROM userinfo"]; //rs=[database executeQuery:@"SELECT * FROM userinfo WHERE Age > ?", @"20"]; while ([rs next]){ NSLog(@"%@ %@",[rs stringForColumn:@"Name"], [rs stringForColumn:@"Age"]); } /* intForColumn: longForColumn: longLongIntForColumn: boolForColumn: doubleForColumn: stringForColumn: dateForColumn: dataForColumn: dataNoCopyForColumn: UTF8StringForColumnIndex: objectForColumn: */ /* 创建图片 一个人有多张照片 create table if not exists photoinfo (ID integer primary key autoincrement, UserID integer, Photo blob); */ sql = @"create table if not exists photoinfo (ID integer primary key autoincrement, UserID integer, Photo blob);";
    [database executeUpdate:sql];

    UIImage *image = [UIImage imageNamed:@"battle_bg4.png"];
    NSData *photoData = UIImagePNGRepresentation(image);
    [database executeUpdate:@"insert into photoinfo (UserID, Photo) values (?, ?);", @"3", photoData];;

    rs = [database executeQuery:@"SELECT * FROM photoinfo;"];  
    while ([rs next]){  
        NSLog(@"%d %d",[rs intForColumn:@"UserID"], [rs intForColumn:@"UserID"]); 
        NSData *d = [rs dataForColumn:@"Photo"];
        [d writeToFile:@"/tmp/test.png" atomically:YES];
    }  
    [database close];
}

代码连接:
https://github.com/leechance/SQLite

资料:
SQLite 数据库学习教程
http://wenku.baidu.com/view/11279ae108a1284ac9504313.html?re=view
全面解析SQLite
http://wenku.baidu.com/view/40d17cd149649b6648d74753.html
MySql 完全教程
http://wenku.baidu.com/view/11279ae108a1284ac9504313.html?re=view