laravel join 子查询 joinSub的源码剖析

发布日期: 2020-09-24

文章字数: 716

想实现join中使用子查询的需求，于是根据文档以及源码寻找方法

想要实现的原生sql

SELECT
*
FROM
    `a`
    LEFT JOIN ( SELECT * FROM `b` WHERE `type` = 2 ) AS b 
    AND ( `a`.`a` = `b`.`a` AND `a`.`b` = `b`.`b` AND `a`.`c` = `b`.`c` ) 
    OR  ( `a`.`a` = `b`.`a` AND `a`.`b` = `b`.`b` AND `a`.`d` = `b`.`d` )

官方文档给的方法(子查询联接)

您可以使用joinSub，leftJoinSub和rightJoinSub方法加入查询的子查询。这些方法中的每一个都接收三个参数：子查询，其表别名和定义相关列的Closure：

$latestPosts = DB::table('posts')
                   ->select('user_id', DB::raw('MAX(created_at) as last_post_created_at'))
                   ->where('is_published', true)
                   ->groupBy('user_id');

$users = DB::table('users')
        ->joinSub($latestPosts, 'latest_posts', function ($join) {
            $join->on('users.id', '=', 'latest_posts.user_id');
        })->get();

实现方法1：joinSub

$query = DB::table('table_name2')->where('type','=',2);
$info = DB::table('table_name')
            ->joinSub($query,'table_name2', function ($join) {
                $join->on([
                    ['table_name.a', '=', 'table_name2.a'],
                    ['table_name.b', '=', 'table_name2.b'],
                    ['table_name.c', '=', 'table_name2.c'],
                ])->orOn([
                    ['table_name.a', '=', 'table_name2.a'],
                    ['table_name.b', '=', 'table_name2.b'],
                    ['table_name.d', '=', 'table_name2.d'],
                ]);
            })->get();

实现方法2：join+getBindings+addBinding

ps: join+子查询只有用到where的时候才需要addBinding，否则sql语句会只有’?’

$query = DB::table('table_name2')->where('type','=',2);

$info = DB::table('table_name')
            ->join(DB::raw('('.$query->toSql().') as table_name2'), function ($join) use ($query) {
                $join->on([
                    ['table_name.a', '=', 'table_name2.a'],
                    ['table_name.b', '=', 'table_name2.b'],
                    ['table_name.c', '=', 'table_name2.c'],
                ])->orOn([
                        ['table_name.a', '=', 'table_name2.a'],
                        ['table_name.b', '=', 'table_name2.b'],
                        ['table_name.d', '=', 'table_name2.d'],
                    ])->addBinding($query->getBindings());
            })->get();

源码剖析joinSub方法

文件地址：/vendor/laravel/framework/src/Illuminate/Database/Query/Builder.php

/**
  * AddHoneycombLog a subquery join clause to the query.
  *
  * @param  \Closure|\Illuminate\Database\Query\Builder|string  $query
  * @param  string  $as
  * @param  \Closure|string  $first
  * @param  string|null  $operator
  * @param  string|null  $second
  * @param  string  $type
  * @param  bool  $where
  * @return \Illuminate\Database\Query\Builder|static
  *
  * @throws \InvalidArgumentException
  */
 public function joinSub($query, $as, $first, $operator = null, $second = null, $type = 'inner', $where = false)
 {
      // 结果：query为原生sql，bindings为getBindings的绑定参数
      // createSub方法见下方
     [$query, $bindings] = $this->createSub($query);

     $expression = '('.$query.') as '.$this->grammar->wrapTable($as);

     $this->addBinding($bindings, 'join');

     return $this->join(new Expression($expression), $first, $operator, $second, $type, $where);
 }

 /**
  * Creates a subquery and parse it.
  *
  * @param  \Closure|\Illuminate\Database\Query\Builder|string  $query
  * @return array
  */
 protected function createSub($query)
 {
     // If the given query is a Closure, we will execute it while passing in a new
     // query instance to the Closure. This will give the developer a chance to
     // format and work with the query before we cast it to a raw SQL string.
     if ($query instanceof Closure) {
         $callback = $query;

         $callback($query = $this->forSubQuery());
     }

     return $this->parseSub($query);
 }
 /**
   * Parse the subquery into SQL and bindings.
   *
   * @param  mixed  $query
   * @return array
   *
   * @throws \InvalidArgumentException
   */
  protected function parseSub($query)
  {
      if ($query instanceof self || $query instanceof EloquentBuilder) {
          return [$query->toSql(), $query->getBindings()];
      } elseif (is_string($query)) {
          return [$query, []];
      } else {
          throw new InvalidArgumentException(
              'A subquery must be a query builder instance, a Closure, or a string.'
          );
      }
  }
/**
  * AddHoneycombLog a binding to the query.
  *
  * @param  mixed  $value
  * @param  string  $type
  * @return $this
  *
  * @throws \InvalidArgumentException
  */
  public function addBinding($value, $type = 'where')
  {
      if (! array_key_exists($type, $this->bindings)) {
          throw new InvalidArgumentException("Invalid binding type: {$type}.");
      }

      if (is_array($value)) {
          $this->bindings[$type] = array_values(array_merge($this->bindings[$type], $value));
      } else {
          $this->bindings[$type][] = $value;
      }

      return $this;
  }