Oracle PL/SQL 查询无法编译

Question

谁能告诉我为什么这不会编译？我收到“缺少表达式”错误：

execute immediate  'select CASE WHEN EXISTS ( SELECT 1 from samples where samplecode = :samplecode  and auditflag = 0 and ' || varFilterString || ') then 1 else 0 end  from DUAL'
into varResult
using varSampleCode;

假设所有变量都正确声明。

TIA

Answer 1

execute immediate  'select  count(1) from DUAL
                      where EXISTS
                       ( SELECT 1 from samples
                        where samplecode = :sample code
                          and auditflag = 0 
                          and ' || varFilterString || ')'
into varResult
using varSampleCode;