How To Resolve Mutating Error
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Mutating Trigger In Oracle 11g
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mutating trigger in oracle 10g with example Fix Oracle mutating trigger table errors Oracle Database Tips by Burleson Consulting A mutation table isMutating Trigger With Example
defined as a table that is changing. But in dealing with triggers, it is a table that has the possibility of changing. What this means to a trigger is that oracle mutating trigger pragma autonomous transaction if the trigger reads a table, it can not change the table that it read from. This does not impact the exclusive use of :OLD and :NEW. It says that if the trigger reads the table (such as using a SELECT query), that changes (even using :NEW) will fail. This can also happen when a trigger on a parent table causes mutating table error in oracle 11g with example an insert on a child table referencing a foreign key. Mutating Tables Each new release of the Oracle database reduces the impact of the mutating table error on triggers and they are much less of a problem with Oracle9i and above. If a trigger does result in a mutating table error, the only real option is to rewrite the trigger as a statement-level trigger. Mutating table errors only impact row level triggers. But to use a statement level trigger, some data may need to be preserved from each row, to be used by the statement level trigger. This data can be stored in a PL/SQL collection or in a temporary table. A simple row level trigger that causes a mutating table error can result in a very complicated statement level trigger to achieve the needed result. Here are some important items to remember about triggers. On insert triggers have no :OLD values. On delete triggers have no :NEW values. Triggers do not commit transactions. If a transaction is rolled back, the data changed by the trigger is also rolled back. Commits, ro
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Tags Users Badges Unanswered Ask Question _ Database Administrators Stack Exchange is a question and answer site for database professionals who wish to improve their database skills and learn http://www.dba-oracle.com/t_avoiding_mutating_table_error.htm from others in the community. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top What are the causes and solutions for mutating table errors? up vote 7 down vote favorite 1 I understand mutating table errors http://dba.stackexchange.com/questions/5432/what-are-the-causes-and-solutions-for-mutating-table-errors are caused by a design flaw or problematic query. An old query was recently put into production which throws a mutating table error. Our DBA solved the problem but we do not know how. What exactly causes mutating table errors and how would our DBA have fixed the problem? sql oracle trigger plsql share|improve this question edited Jun 25 '15 at 17:56 Mahi_0707 1033 asked Sep 6 '11 at 8:46 parmanand 112238 add a comment| 3 Answers 3 active oldest votes up vote 13 down vote accepted The most likely cause of a mutating table error is the misuse of triggers. Here is a typical example: you insert a row in table A a trigger on table A (for each row) executes a query on table A, for example to compute a summary column Oracle throws an ORA-04091: table A is mutating, trigger/function may not see it This is an expected and normal behaviour, Oracle wants to protect you from yourself since Oracle guarantees: (i) that each statement is atomic (i.e will either fail or succee
Social Links Printer Friendly About Search 8i | 9i | 10g | 11g | 12c | 13c | Misc | PL/SQL | SQL | RAC https://oracle-base.com/articles/9i/mutating-table-exceptions | WebLogic | Linux Home » Articles » 9i » Here Mutating http://www.akadia.com/services/ora_mutating_table_problems.html Table Exceptions Mutating table exceptions occur when we try to reference the triggering table in a query from within row-level trigger code. In this article I'll present examples of how a mutating table exception might occur and simple methods to get round it. Test Schema Mutating Table Demonstration mutating trigger Solution 1 (Collection in Package Variable) Solution 2 (Global Temporary Table) Test Schema The following schema objects are necessary to run the code in this article. CREATE TABLE tab1 ( id NUMBER(10) NOT NULL, description VARCHAR2(50) NOT NULL ); ALTER TABLE tab1 ADD ( CONSTRAINT tab1_pk PRIMARY KEY (id) ); CREATE SEQUENCE tab1_seq; CREATE TABLE tab1_audit ( id NUMBER(10) NOT NULL, trigger in oracle action VARCHAR2(10) NOT NULL, tab1_id NUMBER(10), record_count NUMBER(10), created_time TIMESTAMP ); ALTER TABLE tab1_audit ADD ( CONSTRAINT tab1_audit_pk PRIMARY KEY (id) ); ALTER TABLE tab1_audit ADD ( CONSTRAINT tab1_audit_tab1_fk FOREIGN KEY (tab1_id) REFERENCES tab1(id) ); CREATE SEQUENCE tab1_audit_seq; Mutating Table Demonstration Let's assume we need to audit the actions on the parent table and for some reason, this involves querying the triggering table. We can demonstrate this with the following package and trigger. We place all our trigger code into a package as follows. CREATE OR REPLACE PACKAGE trigger_api AS PROCEDURE tab1_row_change (p_id IN tab1.id%TYPE, p_action IN VARCHAR2); END trigger_api; / SHOW ERRORS CREATE OR REPLACE PACKAGE BODY trigger_api AS PROCEDURE tab1_row_change (p_id IN tab1.id%TYPE, p_action IN VARCHAR2) IS l_count NUMBER(10) := 0; BEGIN SELECT COUNT(*) INTO l_count FROM tab1; INSERT INTO tab1_audit (id, action, tab1_id, record_count, created_time) VALUES (tab1_audit_seq.NEXTVAL, p_action, p_id, l_count, SYSTIMESTAMP); END tab1_row_change; END trigger_api; / SHOW ERRORS Next we create the row-level trigger itself to catch any changes to the table. CREATE OR REPLACE TRIGGER tab1_ariu_trg AFTER INSERT OR UPDATE ON tab1 FOR EACH
4 ORA-04088: error during execution of trigger 'TRG_GET_ID_APP'. We studied the "Mutating Table" Problem and found the following explanations in the Oracle8i Application Developer's Guide. A mutating table is a table that is currently being modified by an UPDATE, DELETE, or INSERT statement, or it is a table that might need to be updated by the effects of a declarative DELETE CASCADE referential integrity constraint. The restrictions on such a table apply only to the session that issued the statement in progress. For all row triggers, that were fired as the result of a DELETE CASCADE, there are two important restrictions regarding mutating tables. These restrictions prevent a trigger from seeing an inconsistent set of data. The SQL statements of a trigger cannot read from (query) or modify a mutating table of the triggering statement. Example 1 Select in a mutating table from a row trigger (Tested on Oracle 8.1.7) We want to explain this situation on an example. We have two tables "A" and "B". "A" is the master table and "B" the detail table. We specified a foreign key between "B" and "A" with the CASCADE DELETE option. Here are the CREATE statements drop table B; drop table A; create table A ( ida number not null, vala varchar2(10), primary key(ida)); create table B ( idb number, valb varchar2(10), foreign key (idb) references A (ida) on delete cascade) / create or replace trigger b_br after delete on B for each row declare n integer; begin select count(*) into n from A; dbms_output.put_line('there are ' || n || ' rows in A'); dbms_output.put_line('after statment on B'); dbms_output.new_line; end; / insert into A values(1,'Table A'); insert into A values(2,'Table A'); insert into B values(1,'Table B'); insert into B values(1,'Table B'); commit; set serveroutput on; delete from A where idA = 1