How To Avoid Mutating Trigger Error
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Mutating Trigger In Oracle 10g With Example
Fix Oracle mutating trigger table errors Oracle Database Tips by mutating trigger with example Burleson Consulting A mutation table is defined as a table that is changing. But in dealing with triggers, it is a table that has the possibility of changing. What oracle mutating trigger pragma autonomous transaction this means to a trigger is that 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
Oracle Statement Level Trigger
can also happen when a trigger on a parent table causes 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. Trigge
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Oracle Instead Of Trigger
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 http://www.dba-oracle.com/t_avoiding_mutating_table_error.htm and solutions for mutating table errors? up vote 7 down vote favorite 1 I understand 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 http://dba.stackexchange.com/questions/5432/what-are-the-causes-and-solutions-for-mutating-table-errors 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 succeed completely) (ii) that each statement sees a consistent view of the data Most likely when you write this kind of trigger you would expect the query (2) to see the row inserted on (1). This would be in contradiction with both points above since the update is not finished yet (there could be more rows to be inserted). Oracle could return the result consistent with a point in time just before the beginning of the statement but from most of the examples I have seen that try to implement this logic, people see a multi-row statement as a serie of successive steps and expect the statement [2] to see the changes made by the previous steps. Oracle can not return the expected resul
here for a quick overview of the site Help Center Detailed answers to any questions you might http://stackoverflow.com/questions/16182089/table-is-mutating-trigger-function-may-not-see-it-stopping-an-average-grade-fr have Meta Discuss the workings and policies of this site About http://stackoverflow.com/questions/34951730/plsql-trigger-error-is-mutating-trigger-function-may-not-see-it-ora-04091 Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million mutating trigger programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Table is mutating, trigger/function may not see it (stopping an average grade from dropping below 2.5) up vote 1 down vote favorite Here's the problem: Create a trigger that prevents any change to the taking relation that would drop the mutating trigger in overall average grade in any particular class below 2.5. Note: This trigger is not intended to address the average GPA of any given student, but rather it should address the average grade for all grades assigned in a particular class. Here's the schema: Student-schema =(studentnum, name, standing, gpa, major) Class-schema = (schedulenum, semester, department, classnum, days, time, place, enrollment) Instructor-schema = (name, department, office) Teaches-schema = (name, schedulenum, semester) Taking-schema = (studentnum, schedulenum, semester, grade) I'm having a terrible time with these triggers, but here's my attempt to make this work: CREATE OR REPLACE TRIGGER stopChange AFTER UPDATE OR INSERT OR DELETE ON taking REFERENCING OLD AS old NEW AS new FOR EACH ROW DECLARE grd_avg taking.grade%TYPE; BEGIN SELECT AVG(grade) INTO grd_avg FROM taking WHERE studentnum = :new.studentnum AND schedulenum = :new.schedulenum AND semester = :new.semester; IF grd_avg < 2.5 THEN UPDATE taking SET grade = :old.grade WHERE studentnum = :old.studentnum AND schedulenum = :old.schedulenum AND semester = :old.semester; END IF; END; / I'
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up PLSQL Trigger Error. “is mutating, trigger/function may not see it” ORA-04091 [duplicate] up vote 0 down vote favorite This question already has an answer here: ORA-04091: table [blah] is mutating, trigger/function may not see it 4 answers When I declare a trigger in my Oracle database project, I'm getting an error, which says: ERROR at line 1: ORA-04091: table MIHAL277.LEAGUE_GAMES is mutating, trigger/function may not see it ORA-06512: at "MIHAL277.DELETE_UNUSED_GAME", line 4 ORA-04088: error during execution of trigger 'MB358996.DELETE_UNUSED_GAME' Basically I'm creating an academic project for managing boardgame leagues. So there is a Game table and a League table. There's also a League_Games table, which indicates whether a game is available in a League (i.e if the players in the League play this game). A League can decide to stop 'owning' a game and then it's deleted from the League_Games table. But when it happens I want to run a trigger, which checks out if there are still some Leagues that use the game and if not - delete the entry for the particular game from the Game table.' My trigger goes like this: CREATE OR REPLACE TRIGGER delete_unused_game BEFORE DELETE ON League_Games FOR EACH ROW DECLARE deleted_game_count integer; BEGIN SELECT COUNT(*) INTO deleted_game_count FROM League_Games WHERE Game_ID = :OLD.Game_ID; IF deleted_game_count = 0 THEN DELETE FROM Game WHERE ID = :OLD.Game_ID; END IF; END; / So when I delete an entry from Leage_Games, the error appears. What is wrong with this trigger? sql oracle plsql triggers share|improve this question edited Feb 3 at 0:09 asked Jan 22 at 16:41 mihal277 462 marked as duplicate by Tony Andrewsoracle Users with the oracle badge can single-handedly close oracle questions a