Question

任何人都可以解释我为什么会出现无效的标识符错误以及为什么z.cupu变量无法变量？

 ORA-00904: "Z"."CUPU": invalid identifier

select 
 (select listagg(text, ', ') within group (order by kod)
                    from cis_chyby_pu_na_uss 
                    where kod in (
                        select 
                        regexp_substr(t.stav_full, '[^,]+', 1, l.lev) split
                        from PREKLAPANIE_PU_NA_USS_HIST t, (select rownum as lev 
                                                            from dual 
                                                            connect by level <= length (trim(regexp_replace((select stav_full 
                                                                                                            from PREKLAPANIE_PU_NA_USS_HIST h 
                                                                                                            where z.cupu = h.cislo_pu)
------------------------------------------------------------------------------------------------------------------^
                                                                                                            , '[^,]+')))
                                                            ) l

                        where t.cislo_pu = z.cupu
                        and z.stav <> 100)

    )
    from zz_2202 z

Answer 1

with tab as 
(select 1 n from dual)
select * from tab root 
where n in (select child1.n from tab child1 
             where child1.n in (select child2.n from tab child2 
                                 where child2.n = root.n));

行

with tab as 
(select 1 n from dual)
select (select * from tab child1 where child1.n = root.n)
from tab root;

行

with tab as 
(select 1 n from dual)
select (select * from (select * from tab child2 where child2.n = root.n))
from tab root;

ERROR

因此，在选择列表中嵌套的限制似乎等于1.

Oracle在嵌套子查询时执行相关子查询引用一个引用父语句的表中的列子查询之上的级别。父语句可以是SELECT，子查询嵌套的UPDATE或DELETE语句。一个相关子查询在概念上针对每一行进行一次评估由父语句处理。但是，优化器可能会选择将查询重写为连接或使用其他一些技术制定在语义上等效的查询。 Oracle解决了子查询中的非限定列，通过查看名为的表来查找子查询，然后在父语句中命名的表中。

通过PLSQL连接到连接变量

1 个答案: