SQL查询问题，嵌套查询? 400 报错

SQL查询问题，嵌套查询? 400 报错

Select JNAME FROM J WHERE JNO=(SELECT JNO FROM SPJ WHERE SPJ.SNO=(SELECT SNO FROM S WHERE CITY='上海'))

首先抛开最外层开里面的层，查询结果是       JNO

                                                          J4

                                                          J1

                                                          J2

                                                          J4

然后通过最外层的查询这4个JNO，结果出来是JNAME

                                                          造船厂

可理论结果应该是JNAME

                       造船厂

                        一汽

                         三建

求解 哪里出错了、、