ORA-01756：引用的字符串未在更新查询中正确终止

Question

delete table(select c.investment from clientt c where c.cname='Jhon smith')i
where i.company=(select ref(s) from stockk s where s.company='INFOSYS');

insert into table(select c.investment from clientt c where c.cname='Jill Brody')i
values (investment_ty ((select ref(s) from stockk s where s.company='GM'),64.00,'11-AUG-2001',1000));

问题： -

假设Jhon将他的INFOSYS股票卖给Jill，而Jill今天以现价将她的GM股票卖给了Jhon。更新这两个事务的数据库。

谢谢。