Oracle唯一索引功能替代

Oracle唯一索引在字段全部为NULL时，不做唯一性判断，允许重复插入，而在8t中即使均为NULL值也会做重复值判断，在某些场景下客户会存在此类需求，在数据量不大不存在性能问题的情况下可以考虑通过如下方式进行替代

示例表

create table "informix".secconstitute 
  (
    id decimal(20,0) not null ,
    code varchar(32),
    name varchar(64),
    sec_id decimal(20,0),
    meas_id decimal(20,0),
    constitute_type decimal(10,0),
    order_no decimal(10,0),
    meas_value decimal(22,6),
    ttc_therm decimal(22,6),
    region_id decimal(10,0),
    replicate_flag decimal(10,0),
    download_region decimal(10,0),
    operator_str varchar(64),
    factor_str varchar(64),
    if_reverse decimal(3,0),
    condi_type decimal(10,0),
    primary key (id)  constraint "informix".pk_secconstitute
  ) extent size 64 next size 64 lock mode row;

revoke all on "informix".secconstitute from "public" as "informix";


create unique index "informix".idx_secid_measid_constitutetype_orderno 
    on "informix".secconstitute (sec_id,meas_id,constitute_type,
    order_no) using btree  in dbs3;

思路
1.删除原唯一索引替换为普通索引维持索引功能
2.通过触发器调用SPL进行非NULL值的唯一性判断，必要时中止操作

代码如下

drop index if exists index_438_1;
create index index_438_1 on secconstitute(sec_id,meas_id,constitute_type,order_no);

drop procedure if exists p4_ti_secconstitute_proc;
create procedure p4_ti_secconstitute_proc() referencing new as new for secconstitute

define v_str varchar(100);
define v_col varchar(100);
define v_sql lvarchar(500);
define v_count int8;
define v_flag int;

let v_col='';
let v_str='';
let v_count=0;
let v_sql='';

if new.sec_id is not null or new.meas_id is not null or new.constitute_type is  not null or  new.order_no is not null then
if new.sec_id is not null then
let v_col='sec_id';
let v_str='sec_id='||new.sec_id;
else
let v_col='sec_id';
let v_str='sec_id is null';
end if;

if new.meas_id is not null then
    if v_col != '' then
     let v_col=v_col||','||'meas_id'; 
     else 
     let v_col='meas_id';
    end if;
    if v_str != '' then
     let v_str=v_str||' and meas_id='||new.meas_id;
    else 
     let v_str='meas_id='||new.meas_id;
  end if;
else 
    if v_col != '' then
     let v_col=v_col||','||'meas_id'; 
     else 
     let v_col='meas_id';
    end if;
     if v_str != '' then
     let v_str=v_str||' and meas_id is null';
    else 
     let v_str='meas_id is null';
  end if;
end if;

if new.constitute_type is not null then
    if v_col != '' then
     let v_col=v_col||','||'constitute_type';
     else
     let v_col='constitute_type';
    end if;
    if v_str != '' then
     let v_str=v_str||' and constitute_type='||new.constitute_type;
    else
     let v_str='constitute_type='||new.constitute_type;
  end if;
else
     if v_col != '' then
     let v_col=v_col||','||'constitute_type';
     else
     let v_col='constitute_type';
    end if;
     if v_str != '' then
     let v_str=v_str||' and constitute_type is null';
    else
     let v_str='constitute_type is null';
  end if;
end if;

if new.order_no is not null then
    if v_col != '' then
     let v_col=v_col||','||'order_no';
     else
     let v_col='order_no';
    end if;
    if v_str != '' then
     let v_str=v_str||' and order_no='||new.order_no;
    else
     let v_str='order_no='||new.order_no;
  end if;
else
     if v_col != '' then
     let v_col=v_col||','||'order_no';
     else
     let v_col='order_no';
    end if;
     if v_str != '' then
     let v_str=v_str||' and order_no is null';
    else
     let v_str='order_no is null';
  end if;
end if;

if v_str != '' then
let v_sql='select count(*) from secconstitute where '||v_str||' group by '||v_col;
prepare p from v_sql;
declare c cursor for p;
open c;
fetch c into v_count;
free p;
close c;
free c;
end if;
if v_count >1 then
raise exception -746,0,'Duplicated Sec_Id,Meas_Id,Constitue_Type,Order_No Value Founded!!';
end if;
end if;

end procedure;