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 mutating trigger 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 fix a mutating error?

Fixing the mutating table error

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

What is a mutating table in Oracle?

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.

What is mutating in the trigger Please select all the correct answers?

Mutating trigger is trigger that is currently being modified by DML opertion. For eg.,You created a trigger trigger1 on table1, it should fire after update for each row.

What is mutating error in trigger?

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 Pragma AUTONOMOUS_TRANSACTION in trigger?

The AUTONOMOUS_TRANSACTION pragma changes the way a subprogram works within a transaction. A subprogram marked with this pragma can do SQL operations and commit or roll back those operations, without committing or rolling back the data in the main transaction.

What are triggers in Oracle?

A trigger is either a stored PL/SQL block or a PL/SQL, C, or Java procedure associated with a table, view, schema, or the database itself. Oracle Database automatically executes a trigger when a specified event takes place, which may be in the form of a system event or a DML statement being issued against the table.

What is ref cursor in Oracle with example?

A REF CURSOR is a PL/SQL data type whose value is the memory address of a query work area on the database. In essence, a REF CURSOR is a pointer or a handle to a result set on the database. REF CURSOR s are represented through the OracleRefCursor ODP.NET class.

What is dynamic SQL in Oracle with example?

For example, dynamic SQL lets you create a procedure that operates on a table whose name is not known until runtime. Oracle includes two ways to implement dynamic SQL in a PL/SQL application: Native dynamic SQL, where you place dynamic SQL statements directly into PL/SQL blocks.

What is Dynamic SQL example?

For example, dynamic SQL lets you create a procedure that operates on a table whose name is not known until runtime. In past releases of Oracle, the only way to implement dynamic SQL in a PL/SQL application was by using the DBMS_SQL package.

What is static and dynamic SQL?

Static SQL is SQL statements in an application that do not change at runtime and, therefore, can be hard-coded into the application. Dynamic SQL is SQL statements that are constructed at runtime; for example, the application may allow users to enter their own queries.

What is collection in Oracle with example?

PL/SQL – Collections

Collection Type Number of Elements Where Created
Associative array (or index-by table) Unbounded Only in PL/SQL block
Nested table Unbounded Either in PL/SQL block or at schema level
Variablesize array (Varray) Bounded Either in PL/SQL block or at schema level

How many types of collections are there in Oracle?

three

Oracle provides three basic collections, each with an assortment of methods.

What is the difference between record and collection in Oracle?

To create a collection variable, you either define a collection type and then create a variable of that type or use %TYPE . In a record, the internal components can have different data types, and are called fields.

How can I delete duplicate records in Oracle?

After “SQL,” enter “select rowid, name from names;.” Delete the duplicate. After “SQL,” enter “delete from names a where rowid > (select min(rowid) from names b where b.name=a.name);” to delete duplicate records. Check for duplicates.

What is difference between Rownum and Rowid?

ROWNUM is representative of the sequence allocated to any data retrieval bunch. ROWID is the permanent identity or address of a row. ROWNUM is a temporarily assigned sequence to a row. ROWID is a 16-digit Hexadecimal number in the format BBBBBBBB.

What are pseudo columns in Oracle?

A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. A pseudocolumn is also similar to a function without arguments (please refer to Chapter 5, “Functions”.

What is rank and Dense_rank in Oracle?

Description. The Oracle/PLSQL DENSE_RANK function returns the rank of a row in a group of rows. It is very similar to the RANK function. However, the RANK function can cause non-consecutive rankings if the tested values are the same. Whereas, the DENSE_RANK function will always result in consecutive rankings.

What is difference between rank () ROW_NUMBER () and Dense_rank () in Oracle?

Difference between row_number vs rank vs dense_rank

The row_number gives continuous numbers, while rank and dense_rank give the same rank for duplicates, but the next number in rank is as per continuous order so you will see a jump but in dense_rank doesn’t have any gap in rankings.

What is lead and lag in SQL?

The LEAD function is used to access data from SUBSEQUENT rows along with data from the current row. The LAG function is used to access data from PREVIOUS rows along with data from the current row. An ORDER BY clause is required when working with LEAD and LAG functions, but a PARTITION BY clause is optional.

Which is better rank or Dense_rank?

rank and dense_rank are similar to row_number , but when there are ties, they will give the same value to the tied values. rank will keep the ranking, so the numbering may go 1, 2, 2, 4 etc, whereas dense_rank will never give any gaps.

What is Denserank () and RANK ()?

RANK and DENSE_RANK will assign the grades the same rank depending on how they fall compared to the other values. However, RANK will then skip the next available ranking value whereas DENSE_RANK would still use the next chronological ranking value.

What is SQL partitioning?

Partitioning in SQL Server divides the information into the smaller storage groups; It is about table data and indexes. Partition function can be used with the table column when a table creates. A partition can be defined with the name and its storage attributes.