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POOracle 10g and data validation in a trigger before row update
 

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  1. POOracle 10g and data validation in a trigger before row update
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    <p>I am using Oracle 10g and I have the following table:</p> <pre><code>create table DE_TRANSFORM_MAP ( DE_TRANSFORM_MAP_ID NUMBER(10) not null, CLIENT NUMBER(5) not null, USE_CASE NUMBER(38) not null, DE_TRANSFORM_NAME VARCHAR2(100) not null, IS_ACTIVE NUMBER(1) not null ) </code></pre> <p>That maps to an entry in the following table:</p> <pre><code>create table DE_TRANSFORM ( DE_TRANSFORM_ID NUMBER(10) not null, NAME VARCHAR2(100) not null, IS_ACTIVE NUMBER(1) not null ) </code></pre> <p>I would like to enforce the following rules:</p> <ul> <li>Only one row in DE_TRANSFORM_MAP with the same CLIENT and USE_CASE can have IS_ACTIVE set to 1 at any time</li> <li>Only one row in DE_TRANSFORM with the same NAME and IS_ACTIVE set to 1 at any time</li> <li>A row in DE_TRANSFORM cannot have IS_ACTIVE changed from 1 to 0 if any rows in DE_TRANSFORM_MAP have DE_TRANSFORM_NAME equal to NAME and IS_ACTIVE set to 1</li> </ul> <p>Does this make sense?</p> <p>I have tried to write a stored proc that handles this:</p> <pre><code>create or replace trigger DETRANSFORMMAP_VALID_TRIG after insert or update on SERAPH.DE_TRANSFORM_MAP for each row declare active_rows_count NUMBER; begin select count(*) into active_rows_count from de_transform_map where client = :new.client and use_case = :new.use_case and is_active = 1; if :new.is_active = 1 and active_rows_count &gt; 0 then RAISE_APPLICATION_ERROR(-20000, 'Only one row with the specified client, use_case, policy_id and policy_level may be active'); end if; end; </code></pre> <p>When I do the following it works as expected, I get an error:</p> <pre><code>insert into de_transform_map (de_transform_map_id, client, use_case, de_transform_name, is_active) values (detransformmap_id_seq.nextval, 6, 0, 'TEST', 1); insert into de_transform_map (de_transform_map_id, client, use_case, de_transform_name, is_active) values (detransformmap_id_seq.nextval, 6, 1, 'TEST', 1); </code></pre> <p>But if I then do this:</p> <pre><code>update de_transform_map set use_case = 0 where use_case = 1 </code></pre> <p>I get the following:</p> <pre><code>ORA-04091: table DE_TRANSFORM_MAP is mutating, trigger/function may not see it </code></pre> <p>How can I accomplish my validation?</p> <p>EDIT: I marked Rene's answer as correct because I think the most correct and elegant way to do this is with a compound trigger but our production DB is still just 10g, we are updating to 11g early next year and I will rewrite the trigger then. Until then, I have a blanket trigger that will assert that no rows are duplicated, here it is:</p> <pre><code>create or replace trigger DETRANSFORMMAP_VALID_TRIG after insert or update on DE_TRANSFORM_MAP declare duplicate_rows_exist NUMBER; begin select 1 into duplicate_rows_exist from dual where exists ( select client, use_case, count(*) from de_transform_map where is_active = 1 group by client, use_case having count(*) &gt; 1 ); if duplicate_rows_exist = 1 then RAISE_APPLICATION_ERROR(-20000, 'Only one row with the specified client, use_case may be active'); end if; end; </code></pre>
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