Postgres Count with groupby（jpaを使用）

Question

私はmariaDBを使用しています。今はpostgresに移動しています。 iは、JPA

select count(<primarykeycolumn>) from tablename where condition 

でクエリを持っていますが、Postgresはgroup by句が必要とされているというエラーを与えます。

私はグループを追加したくないので、コードはmariaDBで起動しています。

Internal Exception: org.postgresql.util.PSQLException: ERROR: column "app_movie_summary.creationdate" must appear in the GROUP BY clause or be used in an aggregate function 
    Position: 55 
Error Code: 0 
Call: SELECT COUNT(id) FROM mytable ORDER BY CREATIONDATE DESC 
Query: ReportQuery(name="App_Movie_Summary.findAllByCreationDateCount" referenceClass=App_Movie_Summary sql="SELECT COUNT(Id) FROM mytable ORDER BY CREATIONDATE DESC") 
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:340) 
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:684) 
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:560) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:2055) 
    at org.eclipse.persistence.sessions.server.ServerSession.executeCall(ServerSession.java:570) 
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:242) 
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:228) 
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeSelectCall(DatasourceCallQueryMechanism.java:299) 
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.selectAllRows(DatasourceCallQueryMechanism.java:694) 
    at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.selectAllRowsFromTable(ExpressionQueryMechanism.java:2740) 
    at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.selectAllReportQueryRows(ExpressionQueryMechanism.java:2677) 
    at org.eclipse.persistence.queries.ReportQuery.executeDatabaseQuery(ReportQuery.java:852) 
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:904) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:1134) 
    at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:460) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1222) 
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2896) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1857) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1839) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1804) 
    at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:258) 
    at org.eclipse.persistence.internal.jpa.QueryImpl.getSingleResult(QueryImpl.java:521) 
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:400) 

Answer 1

PostgreSQLでは、あなたは集約関数を混在させることはできません（countのような）非凝集列（creationdates）あなたGROUP BY凝集していない列でない限りで：以下

はエラーです。この場合、グループ化する必要はありません。なぜなら、あなたは ORDER BY creationdateの必要がないからです。注文は count(*)とは関係ありません。このクエリは、完全に有効です：

SELECT count(*) FROM mytable 

あなたはcreationdateが含またくない場合は、必見GROUP BYそれは。あなたがそれを行うと、ORDER BYも再理にかなって：

SELECT creationdate, count(*) from mytable 
GROUP BY creationdate 
ORDER BY creationdate