我也有类似的问题。请确保CAR_LOAN_INSTALLMENT数据块具有以下属性（这有助于我解决问题）：
数据库数据块：是的
允许查询：是的
查询数据源类型：FROM子句查询
查询数据源名称：输入表/视图名称或SELECT查询
假设REGCODE是一个数字，而不是VARCHAR 2。如果是后者，请确保在动态查询中将其括在单引号中（即上面的Q）。
致上，
吉里什

Block Name : CAR_LOAN_INSTALLMENT
Set the properties for this block as follows:

1. Database Data Block: Yes
   Query Allowed: Yes
   Query Data Source Type: FROM clause query

2. Keep the below Query in your Query Data Source Name of the Block  CAR_LOAN_INSTALLMENT.

( May be you are equating with null value.)
Use NVL(:LOAN_SYSTEM.REGCODE,0) --Assuming REGCODE as Number. 
If its Varchar2 then use NVAL(:LOAN_SYSTEM.REGCODE,'N/A')
----------------------------------------------------------------------

SELECT ROW_NUMBER () OVER (ORDER BY ROWNUM) SR, LN_DT, PER_MNTH, DEP_CR,
         FIRST_VALUE (LOAN_AMOUNT - DOWN_PAYMENT) OVER (ORDER BY ROWNUM)
       - SUM (PER_MNTH + DEP_CR) OVER (ORDER BY ROWNUM) BALANCE
  FROM (SELECT CAR_LOAN.REGCODE, ROW_NUMBER () OVER (ORDER BY ROWNUM) SR,
               LN_DT, PER_MNTH, CASE
                  WHEN ROWNUM >= 49
                     THEN 0
                  ELSE DEP_CR
               END DEP_CR, LOAN_AMOUNT, DOWN_PAYMENT
          FROM CAR_LOAN, TABLE (LOANINST (CAR_LOAN.LOAN_DATE)))

注意：检查查询是否按预期返回任何结果。

3. Default Where caluse of Block Property keep it as follows:

    REGCODE = NVL(:LOAN_SYSTEM.REGCODE,0)

4. Write a trigger to execute Query

   GO_BLOCK('CAR_LOAN_INSTALLMENT');
   Clear_Block;
   EXECUTE_QUERY;

Note: Also Check the Table Function/Pipelined Function used in the Query (TABLE (LOANINST (CAR_LOAN.LOAN_DATE)).