Defines a formula (derived value) which is a SQL fragment that acts as a @Column alternative in most cases. Represents read-only state. In certain cases @ColumnTransformer might be a better option, especially as it leaves open the option of still being writable.

    // perform calculations
    @Formula( "sub_total + (sub_total * tax)" )
    long getTotalCost() { ... }

    // call database functions ( e.g. MySQL upper() and substring() )
    @Formula( "upper( substring( middle_name, 1 ) )" )
    Character getMiddleInitial() { ... }

    // this might be better handled through @ColumnTransformer
    @Formula( "decrypt(credit_card_num)" )
    String getCreditCardNumber() { ... }