Dynamic Select with error in where conditon
Whatever value of @P_SqlList the final WHERE sentence will be something like:

WHERE [SOME_FIELD] = @P_Input


due you are setting it here: 

SET @P_Input='@P_Input'


To solve this, add @P_Inputto the parameters list. Or, build the whole filter outside the dynamic query and pass it as a single value:

WHERE ' + @Filter


This form allow you to build a more complicated WHERE sentence.