PostgreSQL查询过滤掉Java中的空Collection

Question

而不是写入

.filter(tableADao -> tableADao.tableBDaos().isEmpty())

我想写一个postgreSQL查询来删除空集合。我想我需要写一个join，后面跟着IS NOT EMPTY。这是怎么写的？

在表A中，我有

@Id
@Column(name = "id_pop", nullable = false)
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@OneToMany(mappedBy = "tableADao", cascade = CascadeType.ALL, orphanRemoval = true)
private Collection<TableBDao> tableBDaos = new ArrayList<>();

在表B中，我有

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "crr_pop_id", nullable = false)
private TableADao tableADao;

Answer 1

尝试

select * from A a 
where 0 < (select count(*) from B b where a.id_pop = b.crr_pop_id )