Caused exception message is:ora-12704: Character Set mismatch

The problem is that when you combine the two result sets of a SELECT query with union ALL, the type of a field appears

is caused by an inconsistency with the type of the corresponding field.

Because the SQL is relatively long, one field is excluded. Finally found

Field Bizdate:select to_char (fbizdate, ' Yyyy-mm-dd hh24:mi:ss ') as bizdate---itself fbizdate is a datetime type character type

Field * * *: SELECT Snumber----Snumber does not know that its data type can be definitely a character but does not know whether it is char or varchar

The problem arises:

e.g:

Select To_char (fbizdate, ' yyyy-mm-dd hh24:mi:ss ')

UNION ALL

Select Snumber

Always thought Snumber was a character type, but it was a character type, but the character also had Char,varchar

So I made a mistake. Since the above is converted to char then the following fields must also convert to char i.e. to_char (snumber)

Suddenly discovering the database is really annoying.