Firebird - 获取触发器内的所有修改字段

Question

我需要获得连续更改的所有值,并在其他"审计"表上发布修改.我是否可以完成此操作,而无需为行中的每个元素编写条件？我知道来自http://www.firebirdfaq.org/faq133/的SQL,它为您提供了验证的所有条件:

select 'if (new.' || rdb$field_name || ' is null and old.' ||
rdb$field_name || ' is not null or new.' || rdb$field_name ||
'is not null and old.' || rdb$field_name || ' is null or new.' ||
rdb$field_name || ' <> old.' || rdb$field_name || ') then'
from rdb$relation_fields
where rdb$relation_name = 'EMPLOYEE';

但这应该写在触发器中.所以,如果我改变一个表,那么我需要修改触发器.

由于FireBird不允许动态增加varchar变量的大小,因此在将其插入文本blob之前,我考虑将所有值转换并连接到一个大的varchar变量.

有没有可能在不使用GTT的情况下实现这一目标？

Answer 1

您需要一些元编程,但在系统表上使用触发器没有问题.

即使您有很多列,此解决方案似乎也可以使用.

set term ^ ;

create or alter procedure create_audit_update_trigger (tablename char(31)) as
    declare sql blob sub_type 1;
    declare fn char(31);
    declare skip decimal(1);
begin
    -- TODO add/remove fields to/from audit table

    sql = 'create or alter trigger ' || trim(tablename) || '_audit_upd for ' || trim(tablename) || ' after update as begin if (';

    skip = 1;
    for select rdb$field_name from rdb$relation_fields where rdb$relation_name = :tablename into :fn do
    begin
        if (skip = 0) then sql = sql || ' or ';
        sql = sql || '(old.' || trim(:fn) || ' is distinct from new.' || trim(:fn) || ')';
        skip = 0;
    end
    sql = sql || ') then insert into ' || trim(tablename) || '_audit (';

    skip = 1;
    for select rdb$field_name from rdb$relation_fields where rdb$relation_name = :tablename into :fn do
    begin
        if (skip = 0) then sql = sql || ',';
        sql = sql || trim(:fn);
        skip = 0;
    end
    sql = sql || ') values (';

    skip = 1;
    for select rdb$field_name from rdb$relation_fields where rdb$relation_name = :tablename into :fn do
    begin
        if (skip = 0) then sql = sql || ',';
        sql = sql || 'new.' || trim(:fn);
        skip = 0;
    end
    sql = sql || '); end';

    execute statement :sql;
end ^

create or alter trigger field_audit for rdb$relation_fields after insert or update or delete as
begin
    -- TODO filter table name, don't include system or audit tables
    -- TODO add insert trigger
    execute procedure create_audit_update_trigger(new.rdb$relation_name);
end ^

set term ; ^