数据库应用

1.建工程，在工程中添加sql外包，如图所示,选择第二个libsqlite3.tbd

2.创建一个桥接文件

command+n创建Header File，在里面写#import <sqlite3.h>

3.获取document路径

let doc=NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
        let sqlPath=doc+"/Student.sqlite"
        print(sqlPath)

4.打开数据库，如果没有创建

//定义为全局变量
var db:OpaquePointer?=nil 
if sqlite3_open(sqlPath,&db) == SQLITE_OK {
            print("数据库打开")
        }

5.创建表

let sql = "create table if not exists user (id integer , name text, age integer)"
        //1.数据库 2.sql语句 3.执行结果 4.参数 5.错误信息
        let resdult=sqlite3_exec(db, sql, nil,nil, nil)
        if resdult == SQLITE_OK {
            print("创建表成功")
        }else{
            print("创建表失败")
        }

6.sql语句操作

//插入数据
        sqlite3_exec(db, "insert into user(id,name,age) values(1,'小明',12)",nil, nil, nil)
        if resdult==SQLITE_OK{
            print("插入成功")
        }else{
            print("插入失败")
        }
        //更新
        let updateSql="update user set name='小粒' where name='小明'";
        let resdult1=sqlite3_exec(db, updateSql, nil, nil, nil)
        if resdult1==SQLITE_OK{
            print("更新成功")
        }else{
           print("更新失败")
       }
        //删除
        let deleteSql="delete from user where name='小粒'";
        let resdult2=sqlite3_exec(db,deleteSql, nil, nil, nil)
        if resdult2==SQLITE_OK{
           print("删除成功")
        }else{
            print("删除失败")
        }
         //查找
         let searchSql="select * from user where name=?"
        //1.数据库 2.sql 3.sql长度 -1 自动计算 4.伴随指针 5.nil
        var stmt:OpaquePointer?=nil
        let resdult3=sqlite3_prepare_v2(db, searchSql,-1, &stmt, nil)
        //给？赋值
        //1.伴随指针 2.？在第几位 从1开始 3.绑定的值
        sqlite3_bind_int(stmt, 2, 1)
        //将SQLITE_TRANSIENT定义为全局变量
            private let SQLITE_TRANSIENT = unsafeBitCast(-1, to:     sqlite3_destructor_type.self)
        sqlite3_bind_text(stmt, 1, "小明", -1, SQLITE_TRANSIENT)
        if resdult3==SQLITE_OK{
                       print("预编译成功")
                   }else{
                       print("预编译失败")
                    }
        //执行sql
        while sqlite3_step(stmt) == SQLITE_ROW{
            //取值
            let id=sqlite3_column_int(stmt, 0)
            let cname=sqlite3_column_text(stmt, 1)
            let name=String(cString: cname!)
            let age=sqlite3_column_int(stmt,2)
            print("id=\(id),name=\(name),age=\(age)")
            //把对象装到数组中
        }
        //释放stmt
        sqlite3_finalize(stmt)
        //关闭数据库
        sqlite3_close(db)