Question: What Is A Mutating Table?

How many triggers can be applied to a table?

There are 12 types of triggers can exist in a table in Oracle: 3 before statement, 3 after statement, 3 before each row and 3 after each row.

On a single table you can define as many triggers as you need..

What is bulk collect in Oracle?

A bulk collect is a method of fetching data where the PL/SQL engine tells the SQL engine to collect many rows at once and place them in a collection. The SQL engine retrieves all the rows and loads them into the collection and switches back to the PL/SQL engine.

What is Oracle Pragma?

A pragma is a compiler directive that is processed at compile time, not at run time. About: In PL/SQL, the pragma EXCEPTION_INIT tells the compiler to associate an exception name with an Oracle Database error number. That lets you refer to any internal exception by name and to write a specific handler for it.

Is commit needed after insert?

So yes, by default, if you’re just using INSERT , the records you insert will be committed, and there is no point trying to roll them back. (This is effectively the same as wrapping each statement between BEGIN and COMMIT .)

What are types of triggers in Oracle?

There are five different types of Oracle Database triggers.Statement triggers are associated with a DML statement, such as DELETE , INSERT , or UPDATE , on a specified table or view. … Row triggers are fired for each row that is affected by an INSERT , UPDATE , or DELETE statement on a table.More items…

Which cursor is faster in Oracle?

The output from the procedure clearly demonstrates that implicit cursors are faster than explicit cursors. The interesting thing is that the implicit cursor is not only faster, but it is actually doing more work, since it includes a NO_DATA_FOUND and a TOO_MANY_ROWS exception check.

What is mutating table in Oracle with example?

A mutating table error (ORA-04091) occurs when a row-level trigger tries to examine or change a table that is already undergoing change (via an INSERT, UPDATE, or DELETE statement). In particular, this error occurs when a row-level trigger attempts to read or write the table from which the trigger was fired.

How do you avoid mutating errors?

In this trigger:First, declare an array of customer record that includes customer id and credit limit.Second, collect affected rows into the array in the row-level trigger.Third, update each affected row in the statement-level trigger.

Can we use commit inside a trigger in Oracle?

Not only do triggers not need a COMMIT you can’t put one in: a trigger won’t compile if the body’s code includes a COMMIT (or a rollback). This is because triggers fire during a transaction. When the trigger fires the current transaction is still not complete.

How do you commit inside a trigger?

Yes, you can commit inside the trigger. But for this you have to make this trigger transaction to be an Independent transaction from its parent transaction, you can do this by using Pragma. Pragma AUTONOMOUS_TRANSACTION allow you to build the Independent (child) Transaction, started by another.

How many triggers are possible per table in SQL?

There can be only one first or last trigger for each statement on a table.

What is ref cursor in Oracle?

Using REF CURSOR s is one of the most powerful, flexible, and scalable ways to return query results from an Oracle Database to a client application. A REF CURSOR is a PL/SQL data type whose value is the memory address of a query work area on the database. … A REF CURSOR refers to a memory address on the database.

What is the meaning of mutating?

verb (used with object), mu·tat·ed, mu·tat·ing. to change; alter. Biology. to cause (a gene, cell, etc.) to undergo an alteration of one or more characteristics: The disease mutates the retina’s rod cells, and they slowly stop working. Phonetics. to change by umlaut.

Which triggers are used for virtual tables?

A common use of Magic tables in SQL Server is the DML (Data Manipulation Language) trigger. SQL Server DML trigger allows using these two virtual tables INSERTED and DELETED.

What is materialized view in Oracle?

A materialized view is a database object that contains the results of a query. The FROM clause of the query can name tables, views, and other materialized views. … You can select data from a materialized view as you would from a table or view.

Why bulk collect is faster in Oracle?

Since the BULK COLLECT fetches the record in BULK, the INTO clause should always contain a collection type variable. The main advantage of using BULK COLLECT is it increases the performance by reducing the interaction between database and PL/SQL engine.

How do you avoid mutating table errors?

Avoiding Mutating triggers The Oracle mutating trigger error occurs when a trigger references the table that owns the trigger, resulting in the “ORA-04091: table name is mutating, trigger/function may not see it.” message. Don’t use triggers – The best way to avoid the mutating table error is not to use triggers.

What is instead of trigger in Oracle?

What is an instead of trigger in Oracle. An INSTEAD OF trigger is a trigger that allows you to update data in tables via their view which cannot be modified directly through DML statements. When you issue a DML statement such as INSERT , UPDATE , or DELETE to a non-updatable view, Oracle will issue an error.

Can rollback or commit issued inside a trigger code?

Changes made within triggers should thus be committed or rolled back as part of the transaction in which they execute. For this reason, triggers are NOT allowed to execute COMMIT or ROLLBACK statements (with the exception of autonomous triggers).

What is the maximum number of triggers a database can have?

There is no limit. U can create as many as u want. But in practice you wont create more than 6 or 7 triggers.

How do you handle exceptions in bulk collect?

Key components of bulk DML with exception handling:A collection variable to hold the data.The FORALL construct which iterates through values in the collection variable.The SAVE EXCEPTIONS clause which tracks the exceptions being raised during bulk DML.More items…•