Revisionshistorik for flere tabeller i databasen

Jeg har set en meget effektiv implementering af dette, som går som følger:

TABLE audit_entry (
    audit_entry_id          INTEGER         PRIMARY KEY,
    audit_entry_type        VARCHAR2(10)    NOT NULL,
    -- ^^ stores 'INSERT' / 'UPDATE' -- / 'DELETE'

    table_name              VARCHAR2(30)    NOT NULL,
    -- ^^ stores the name of the table that is changed

    column_name             VARCHAR2(30)    NOT NULL,
    -- ^^ stores the name of the column that is changed

    primary_key_id          INTEGER         NOT NULL,
    -- ^^ Primary key ID to identify the row that is changed

    -- Below are the actual values that are changed.
    -- If the changed column is a foreign key ID then
    -- below columns tell you which is new and which is old
    old_id                  INTEGER,
    new_id                  INTEGER,

    -- If the changed column is of any other numeric type,
    -- store the old and new values here.
    -- Modify the precision and scale of NUMBER as per your 
    -- choice.
    old_number              NUMBER(18,2),
    new_number              NUMBER(18,2),

    -- If the changed column is of date type, with or without
    -- time information, store it here.
    old_ts                  TIMESTAMP,
    new_ts                  TIMESTAMP,

    -- If the changed column is of VARCHAR2 type,
    -- store it here.
    old_varchar             VARCHAR2(2000),
    new_varchar             VARCHAR2(2000),
    ...
    ... -- Any other columns to store data of other types,
    ... -- e.g., blob, xmldata, etc.
    ...
)

Og vi opretter en simpel sekvens for at give os en ny inkrementel heltalsværdi for audit_entry_id :

CREATE SEQUENCE audit_entry_id_seq;

Skønheden ved en tabel som audit_entry er, at du kan gemme information om alle typer DML'er- INSERT , UPDATE og DELETE samme sted.

For f.eks. at indsætte, behold old_* kolonner null og udfylder new_* med dine værdier.

For opdateringer skal du udfylde både old_* og new_* kolonner, når de ændres.

For sletning skal du blot udfylde old_* kolonner og behold new_* null.

Og selvfølgelig skal du indtaste den passende værdi for audit_entry_type .;0)

Så har du for eksempel en tabel som følger:

TABLE emp (
    empno           INTEGER,
    ename           VARCHAR2(100) NOT NULL,
    date_of_birth   DATE,
    salary          NUMBER(18,2) NOT NULL,
    deptno          INTEGER -- FOREIGN KEY to, say, department
    ...
    ... -- Any other columns that you may fancy.
    ...
)

Du skal bare oprette en trigger på denne tabel som følger:

CREATE OR REPLACE TRIGGER emp_rbiud
-- rbiud means Row level, Before Insert, Update, Delete
BEFORE INSERT OR UPDATE OR DELETE
ON emp
REFERENCING NEW AS NEW OLD AS OLD
DECLARE
    -- any variable declarations that deem fit.
BEGIN
    WHEN INSERTING THEN
        -- Of course, you will insert empno.
        -- Let's populate other columns.

        -- As emp.ename is a not null column, 
        -- let's insert the audit entry value directly.
        INSERT INTO audit_entry(audit_entry_id,
                                audit_entry_type,
                                table_name,
                                column_name,
                                primary_key,
                                new_varchar)
        VALUES(audit_entry_id_seq.nextval,
               'INSERT',
               'EMP',
               'ENAME',
               :new.empno,
               :new.ename);

        -- Now, as date_of_birth may contain null, we do:
        IF :new.date_of_birth IS NOT NULL THEN
            INSERT INTO audit_entry(audit_entry_id,
                                    audit_entry_type,
                                    table_name,
                                    column_name,
                                    primary_key,
                                    new_ts)
            VALUES(audit_entry_id_seq.nextval,
                   'INSERT',
                   'EMP',
                   'DATE_OF_BIRTH',
                   :new.empno,
                   :new.date_of_birth);
        END IF;

        -- Similarly, code DML statements for auditing other values
        -- as per your requirements.

    WHEN UPDATING THEN
        -- This is a tricky one.
        -- You must check which columns have been updated before you
        -- hurry into auditing their information.

        IF :old.ename != :new.ename THEN
            INSERT INTO audit_entry(audit_entry_id,
                                    audit_entry_type,
                                    table_name,
                                    column_name,
                                    primary_key,
                                    old_varchar,
                                    new_varchar)
            VALUES(audit_entry_id_seq.nextval,
                   'INSERT',
                   'EMP',
                   'ENAME',
                   :new.empno,
                   :old.ename,
                   :new.ename);
        END IF;

        -- Code further DML statements in similar fashion for other
        -- columns as per your requirement.

    WHEN DELETING THEN
        -- By now you must have got the idea about how to go about this.
        -- ;0)
END;
/

Bare et advarselsord:Vær selektiv med hvilke tabeller og kolonner du vælger at revidere, for i hvert fald vil denne tabel have et stort antal rækker. SELECT udsagn på denne tabel vil være langsommere, end du måske forventer.

Jeg ville virkelig elske at se enhver anden form for implementering her, da det ville være en god lærerig oplevelse. Håber dit spørgsmål får flere svar, da dette er den bedste implementering af en revisionstabel, som jeg har set, og jeg leder stadig efter måder at gøre den bedre på.