Avoid illegal character data

Various functions can cause you to create illegal character data. For example, you can produce non-NFC' data by using functions such as trim(), substring(), or others to manipulate the data, or by inserting any code points by using the unichr function, as in the following example:

INSERT INTO test values (unichr(101)||unichr(775));

These actions can result in illegal character content in the database. If you unload that data, you are not able to reload it by using nzload. Unsupported character data can also prevent future upgrades until the characters are changed to supported values.