ThinkPHP5——数据库操作（系统方法）

查询
1. table方法查询数据

   $data = Db::table("user")->select();
//查询一条数据
    $data = Db::table("user")->find();

//进行条件匹配
//单条件查询
    $data = Db::table("user")->where("id", ">", 2)->select();

//多条件查询
    //多条件且查询
    $data = Db::table("user")->where("id", ">", 2)->where("id", "<", 3)->select();
    //字符串形式查询
    $data = Db::table("user")->where("id > 2 and id > 3")->select();
    
    //多条件或查询
    $data = Db::table("user")->where("id", "<=", 5)->whereOr("id", ">=", 2)->select();
    //字符串形式查询
      $data = Db::table("user")->where("id > 2 or id > 3")->select();
 //模糊查询
      $data = Db::table("user")->where("name", "like", "%user1%")->select();

2. limit()方法截取数据：

// 对应的查询语句SELECT * FROM `user` LIMIT 3
$data = Db::table("user")->limit(3)->select();
$data = Db::table("user")->limit(3,3)->select();

3. order()方法对结果集进行排序：

//SELECT * FROM `user` ORDER BY `id`  默认降序
 $data = Db::table("user")->order("id")->select();
 //SELECT * FROM `user` ORDER BY `id` DESC
 $data = Db::table("user")->order("id", "desc")->select();

4. field()方法查询特定字段：

//设置查询字段
 //SELECT `name`,`pass` FROM `user`
 $data = Db::table("user")->field("name,pass")->select();
 //SELECT name unname,`pass` FROM `user`
 $data = Db::table("user")->field("name unname,pass")->select();
//以数组的形式查询特定字段
 //SELECT `name`,`pass` FROM `user`
 $data = Db::table("user")->field(["name", "pass"])->select();

5. 使用数组进行特定字段的条件查询：

//SELECT `name` AS `uname`,`pass` FROM `user`
  $data = Db::table("user")->field(["name"=>"uname", "pass"])->select();
//不查询name  和 pass  SELECT `id`,`age` FROM `user`
  $data = Db::table("user")->field("name, pass", true)->select();

6. group()方法实现分组聚合操作：

//SELECT pass, count(*) total FROM `user` GROUP BY `pass`
  $data = Db::table("user")->field("pass, count(*) total")->group("pass")->select();

7. having()方法实现过滤（注：Having只能结合group一起使用）：

//SELECT pass, count(*) total FROM `user` GROUP BY `pass` HAVING total >= 2
  $data = Db::table("user")->field("pass, count(*) total")->having("total >= 2")->group("pass")->select();

8. join()方法实现多表查询：

//SELECT `goods`.*,type.name tname FROM `goods` INNER JOIN `type` ON `type`.`id`=`goods`.`cid`
  $data = Db::table("goods")->field("goods.*, type.name tname")->join("type", "type.id=goods.cid")->select();

//右连接查询，即需要在join方法中传递第三个参数'right' 右连接  'left'左连接
  $data = Db::table("goods")->field("goods.*, type.name tname")->join("type", "type.id=goods.cid", 'right')->select();
//左连接
  $data = Db::table("goods")->field("goods.*, type.name tname")->join("type", "type.id=goods.cid", 'left')->select();

9. 对查询的表设置自定义名称：

//SELECT `g`.*,t.name tname FROM `goods` `g` LEFT JOIN `type` `t` ON `t`.`id`=`g`.`cid`
        $data = Db::table("goods")->alias("g")->field("g.*, t.name tname")->join("type t", "t.id=g.cid", 'left')->select();

10. 对查询结果集的求和、计数、最大、最小值：

 //SELECT MAX(age) AS tp_max FROM `user` LIMIT 1
    $data = Db::table("user")->max("age");
 //SELECT MIN(age) AS tp_min FROM `user` LIMIT 1
    $data = Db::table("user")->min("age");
 //SELECT AVG(age) AS tp_avg FROM `user` LIMIT 1
     $data = Db::table("user")->avg("age");
 //SELECT SUM(age) AS tp_sum FROM `user` LIMIT 1
     $data = Db::table("user")->sum("age");
 //SELECT COUNT(age) AS tp_count FROM `user` LIMIT 1
     $data = Db::table("user")->count("age");

增加操作
1. insert()方法实现插入一条数据:

//插入数据
       //数组中的字段名 必须和数据库中二点字段名一致
       $data = [
         "name"=>"张三",
         "pass"=>"123",
         "age"=>18
       ];
       //INSERT INTO `user` (`name` , `pass` , `age`) VALUES ('张三' , 123 , 18)
       //返回影响行数
       $code = Db::table("user")->insert($data);

2. insertAll()方法实现插入多条数据:

//即以二维数组的形式作为insertAll()方法的参数
 $data = [
         [
           "name"=>"张三1",
           "pass"=>"123",
           "age"=>18
         ],
         [
           "name"=>"张三2",
           "pass"=>"123",
           "age"=>19
         ]
       ];
       //INSERT INTO `user` (`name` , `pass` , `age`) VALUES ( '张三1','123',18 ) , ( '张三2','123',19 )
       //返回结果影响行数2
       $code = Db::table("user")->insertAll($data);

3. insetrtGetId()方法实现插入并获取插入的主键值（此处指ID）:

 /获取最后一次插入ID
       $data = [
         "name"=>"张三",
         "pass"=>"123",
         "age"=>18
       ];
       // INSERT INTO `user` (`name` , `pass` , `age`) VALUES ('张三' , 123 , 18)
       // string(2) "32"
       //返回值时最后插入的ID
       $code = Db::table("user")->insertGetId($data);

更新数据
1. 修改数据:

// UPDATE `user` SET `pass`=444,`age`=2 WHERE `id` > 25
 // int(14)
 $code = Db::table("user")->where("id", ">", 25)->update(["pass"=>444, "age"=>2]);
 //update()中需以数组的形式进行对相应字段的更新操作

2. setInc()方法实现自增、setDec()方法实现自减:

//实现自增，默认增1
$code = Db::table("user")->where("id", 23)->setInc("age");
//实现自减，修改默认，即此时减3
$code = Db::table("user")->where("id", 23)->setdec("age", 3);

删除数据
1. delete()方法实现删除一条数据:

//DELETE FROM `user` WHERE `id` = 23
   $code = Db::table("user")->where("id", 23)->delete();
 //入如果删除数据和主键有关，那么直接把相应的主键的值放在delete中就行
 //DELETE FROM `user` WHERE `id` = 22
   $code = Db::table("user")->delete(22);

2. 通过in()的方式删除多条数据:

//DELETE FROM `user` WHERE ( id in(20,21) )
  $code = Db::table("user")->where("id in(20,21)")->delete();
 //DELETE FROM `user` WHERE `id` IN (17,18,19)
  $code = Db::table("user")->delete([17, 18, 19]);

3. 通过where条件限制删除区间数据:

//DELETE FROM `user` WHERE ( id > 10 and id <19 )
  $code = Db::table("user")->where("id > 10 and id <19")->delete();