Caused exception message is: ORA-12704: Character Set Mismatch

This problem occurs when Union all is used to merge two result sets of select queries, the type of a field appears.

Different from the type of the corresponding field.

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

Field bizdate: Select to_char (fbizdate, 'yyyy-mm-dd hh24: MI: ss') as bizdate --- fbizdate itself is datetime type to character type

Field ***: Select snumber ---- snumber does not know whether its data type can be a character, but does not know whether it is Char or varchar.

The problem occurs:

E. g:

Select to_char (fbizdate, 'yyyy-mm-dd hh24: MI: ss ')

Union all

Select snumber

I always thought that snumber is a character type, but it is indeed a character type, but also has char, varchar

So I made a mistake. Since the preceding fields are converted to Char, the following fields must also be converted to Char, that is, to_char (snumber)

Suddenly I found the database really annoying ..