How to select from subquery using Laravel Query Builder?

问题

I\'d like to get value by the following SQL using Eloquent ORM.

- SQL

 SELECT COUNT(*) FROM 
 (SELECT * FROM abc GROUP BY col1) AS a;

Then I considered the following.

- Code

 $sql = Abc::from(\'abc AS a\')->groupBy(\'col1\')->toSql();
 $num = Abc::from(\\DB::raw($sql))->count();
 print $num;

I\'m looking for a better solution.

Please tell me simplest solution.

回答1:

In addition to @delmadord's answer and your comments:

Currently there is no method to create subquery in FROM clause, so you need to manually use raw statement, then, if necessary, you will merge all the bindings:

$sub = Abc::where(..)->groupBy(..); // Eloquent Builder instance

$count = DB::table( DB::raw("({$sub->toSql()}) as sub") )
    ->mergeBindings($sub->getQuery()) // you need to get underlying Query Builder
    ->count();

Mind that you need to merge bindings in correct order. If you have other bound clauses, you must put them after mergeBindings:

$count = DB::table( DB::raw("({$sub->toSql()}) as sub") )

    // ->where(..) wrong

    ->mergeBindings($sub->getQuery()) // you need to get underlying Query Builder

    // ->where(..) correct

    ->count();

回答2:

Laravel v5.6.12 (2018-03-14) added fromSub() and fromRaw() methods to query builder (#23476).

The accepted answer is correct but can be simplified into:

DB::query()->fromSub(function ($query) {
    $query->from('abc')->groupBy('col1');
}, 'a')->count();

The above snippet produces the following SQL:

select count(*) as aggregate from (select * from `abc` group by `col1`) as `a`

回答3:

The solution of @JarekTkaczyk it is exactly what I was looking for. The only thing I miss is how to do it when you are using DB::table() queries. In this case, this is how I do it:

$other = DB::table( DB::raw("({$sub->toSql()}) as sub") )->select(
    'something', 
    DB::raw('sum( qty ) as qty'), 
    'foo', 
    'bar'
);
$other->mergeBindings( $sub );
$other->groupBy('something');
$other->groupBy('foo');
$other->groupBy('bar');
print $other->toSql();
$other->get();

Special atention how to make the mergeBindings without using the getQuery() method

回答4:

From laravel 5.5 there is a dedicated method for subqueries and you can use it like this:

Abc::selectSub(function($q) { $q->select('*')->groupBy('col1'); }, 'a')->count('a.*');

Abc::selectSub(Abc::select('*')->groupBy('col1'), 'a')->count('a.*');

回答5:

I could not made your code to do the desired query, the AS is an alias only for the table abc, not for the derived table. Laravel Query Builder does not implicitly support derived table aliases, DB::raw is most likely needed for this.

The most straight solution I could came up with is almost identical to yours, however produces the query as you asked for:

$sql = Abc::groupBy('col1')->toSql();
$count = DB::table(DB::raw("($sql) AS a"))->count();

The produced query is

select count(*) as aggregate from (select * from `abc` group by `col1`) AS a;

回答6:

I like doing something like this:

Message::select('*')
->from(DB::raw("( SELECT * FROM `messages`
                  WHERE `to_id` = ".Auth::id()." AND `isseen` = 0
                  GROUP BY `from_id` asc) as `sub`"))
->count();

It's not very elegant, but it's simple.

来源：https://stackoverflow.com/questions/24823915/how-to-select-from-subquery-using-laravel-query-builder

标签

sql

laravel

laravel-4

eloquent

query-builder