使用IS NULL运算符生成Eclipselink查询

Question

我有3张桌子，RA，CC和EC。 RA有一个外键，＆＃39; ec＆＃39;它映射到＆＃39;代码＆＃39; EC表中的列。 RA还有另一个外键，＆＃39; sc＆＃39;它映射到＆＃39;代码＆＃39; CC表中的列。

@Entity
@NamedQueries({
@NamedQuery( name="getSettingsByCode, query="select object(o) from RA where  o.sc.code = :someCode and o.ec.code is null" )
})

public class RA implements java.io.Serializable {
@Id
private long id;

private Timestamp recupdatetime;

@ManyToOne
@JoinColumn(name="SC")
private Cc sc;

@ManyToOne
@JoinColumn(name="EC")
private Ec ec;

Cc的实体

@Entity

public class Cc {

@OneToMany(mappedBy="sc")
private Set<RA> raCollection;

Ec的实体

@Entity

public class Ec  {

@OneToMany(mappedBy="ec")
private Set<Recommendedalarmsetting> recommendedalarmsettingCollection;

执行namedQuery时，会生成以下sql，

[sql] SELECT t0.ID, t0.RECUPDATETIME, t0.EC, t0.SC FROM RA t0, EC t1 WHERE (
((t0.sc = ?) AND (t1.CODE IS NULL)) AND (t1.CODE = t0.ec))

这个SQL生成是否正确？我不确定IS NULL运算符是否生成了EC表的连接。