doctrine2 - Doctrine 2: Cannot select entity through identification variables without choosing at least one root entity alias -

rather actual question, sticky note myself, may others. there many other similar questions: 1, 2, 3, 4, 5, 6, none of them seems offer solution.

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i have following entities:

class order {     // ...      /**      * @manytoone(targetentity="customer")      * @var customer      */     private $customer;      /**      * @column(type="integer")      * @var int      */     private $amount; }  class customer {     // ... } 

order has unidirectional, many-to-one relationship customer. want every customer, along total amount of orders, run following dql query:

select c, sum(o.amount) model\order o join o.customer c group c 

but following error:

[doctrine\orm\query\queryexception]
[semantical error] line 0, col -1 near 'select c, sum(o.amount)': error: cannot select entity through identification variables without choosing @ least 1 root entity alias.

how can fix it?

this known doctrine limitation.

the solution explicitly select entity want retrieve (customer) , manually join other entity (order) there, using with condition:

select c, sum(o.amount) model\customer c join model\order o o.customer = c group c