Oracle Error Message
PLS-00615: type mismatch found at ‘string’ between CASE operand and WHEN operands
Reason for the Error
In a simple CASE statement or expression, the CASE operand and WHEN operands do not match in datatype, and it is unclear which implicit conversion is required to correct the mismatch.
Solution
Change the CASE operand and WHEN operands so that their datatypes match. Consider using datatype conversion functions in the CASE operand and/or WHEN operands.