I want to implement JPA Projection with count. I tried this:
@Query(value = "SELECT new org.service.PaymentTransactionsDeclineReasonsDTO( id, count(id) as count, status, error_class, error_message) " +
" FROM payment_transactions " +
" WHERE terminal_id = :id AND (created_at > :created_at) " +
" AND (status != 'approved') " +
" GROUP BY error_message " +
" ORDER BY count DESC", nativeQuery = true)
List<PaymentTransactionsDeclineReasonsDTO> transaction_decline_reasons(@Param("id") Integer transaction_unique_id, @Param("created_at") LocalDateTime created_at);
But I get error: Caused by: java.sql.SQLException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '.plugin.service.PaymentTransactionsDeclineReasonsDTO( id, count(id) as c' at line 1
Caused by: java.sql.SQLException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '.plugin.service.PaymentTransactionsDeclineReasonsDTO( id, count(id) as c' at line 1
How I can implement proper count when I have class based Projection?
Try Interface-based Projection instead of DTO:
public interface TransactionDeclineReason {
Integer getId();
Long getCount();
Status getStatus();
ErrorClass getErrorClass(); // I suppose it's enum...
String getErrorMessage();
}
@Query(value = "select " +
"id as id, " +
"count(id) as count, " +
"status as status, " +
"error_class as errorClass, " +
"error_message as errorMessage " +
"from " +
"payment_transactions " +
"where " +
"terminal_id = ?1 " +
"and created_at > ?2 " +
"and status != 'approved' " +
"group " +
"by error_message " +
"order by " +
"2 desc", nativeQuery = true)
List<TransactionDeclineReason> getTransactionDeclineReasons(Integer transactionId, LocalDateTime createdAt);
Pay attention on aliases (ie id as id
) - they are mandatory.
You are mixing JPQL and SQL syntax.
The constructor expression ( new ...
) is JPQL, but in the annotation you mark it as a nativeQuery
ie as SQL so you have to make up your mind.
If it is to be SQL I don't think you can use aliases in the ORDER BY
clause, so you might have to either repeat the expression or wrap it in a subselect as described here: Using an Alias in a WHERE clause .
If it is to be JPQL it doesn't support aliases in a constructor expression, so I guess you have to repeat the expression in the order by clause.
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