to_char() 多了个字符

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sp.param_value nvarchar2(200);

select sp.param_code, to_number(sp.param_value), sp.param_value,length(param_value)
from sys_service_param sp
where sp.param_type_code = 'bank'
and sp.param_value = to_char(0.78,'0.00')

为什么to_char不行呢？
select sp.param_code, to_number(sp.param_value), sp.param_value,length(param_value)
from sys_service_param sp
where sp.param_type_code = 'bank'
发现 param_value 字符长度为4 0.78=4

to_char 格式的是5个字符
SQL> select length(to_char(0.78,'0.00')),to_char(0.78,'0.00') from dual;
LENGTH(TO_CHAR(0.78,'0.00')) TO_CHAR(0.78,'0.00')
---------------------------- --------------------
5 0.78

不带格式的是3个字符
SQL> select length(to_char(0.78)),to_char(0.78) from dual;
LENGTH(TO_CHAR(0.78)) TO_CHAR(0.78)
--------------------- -------------
3 .78

难怪查不到数据呢！！
SQL> select length('0.78') from dual;
LENGTH('0.78')
--------------
4

而这种直接单引号就行

所以 and sp.param_value = trim(to_char(0.78,'0.00')) 就行了

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