PLSQL Language Reference-PL/SQL資料型別-SQL資料型別-使用者定義的PL/SQL子型別

SUBTYPE 子型別名稱 IS 基型別名稱;

SUBTYPE "DOUBLE PRECISION" IS FLOAT;

--給正常型別一個別名，不是什麼好習慣

DECLARE

    SUBTYPE Balance IS NUMBER;

    checking_account        Balance(6,2);

    savings_account         Balance(8,2);

    certificate_of_deposit  Balance(8,2);

    max_insured  CONSTANT   Balance(8,2) := 250000.00;

    SUBTYPE Counter IS NATURAL;

    accounts     Counter := 1;

    deposits     Counter := 0;

    withdrawals  Counter := 0;

    overdrafts   Counter := 0;

    PROCEDURE deposit (

        account  IN OUT Balance,

        amount   IN     Balance

    )

    IS

    BEGIN

        account  := account + amount;

        deposits := deposits + 1;

    END; 

BEGIN

    NULL;

END;