Question

为什么函数中的以下代码调用会产生此错误？

SELECT table0.data
FROM table0
WHERE table0.id IN (SELECT cursor FROM dual);

虽然SELECT cursor FROM dual可以在命令行上运行吗？

Answer 1

虽然SQL * Plus和PL / SQL Developer等客户端能够处理从查询返回的引用游标，如下所示：

select cursor(select 'X' as txt from dual)
from   dual;

SQL where子句要求表达式解析为值或子查询，而不是游标表达式：

select * from dual
where  dummy in 
       ( select cursor(select 'X' as txt from dual)
         from dual );

ERROR at line 3:
ORA-22902: CURSOR expression not allowed

select * from dual
where  dummy in ( cursor(select 'X' as txt from dual) );

ERROR at line 2:
ORA-22902: CURSOR expression not allowed

如果尝试替换返回引用游标的函数，则会出现类似错误（此处testcursor()是一个返回引用游标的函数）：

select * from dual
where  dummy in testcursor();

ERROR at line 2:
ORA-00932: inconsistent datatypes: expected - got CURSOR

这不是where条款处理的事情。

在CURSOR中：预期 - 得到了CURSOR

1 个答案: