Friday, November 2, 2018

Oracle cursor in select statement

Why do you use cursors in Oracle? When you do not need to close a cursor in Oracle? If the enclosing statement is a SELECT statement , nested cursors can also appear in the outermost select list of the query specification or in the outermost select list of another nested cursor.


What are cursors in Oracle? Nested cursors cannot appear in views. I want to run a query, get the and then iterate through the of that query with another select statement using the values of the first statement in my 2nd statement ( cursor ).

I have users in my db. Is it possible to output a SELECT. Oracle creates context area for processing an SQL statement which contains all information about the statement. A cursor holds the rows returned by the SQL statement.


The set of rows the cursor holds is referred as active set. Oracle internally manages the whole execution cycle of implicit cursors and reveals only the cursor ’s information and statuses such as SQL ROWCOUNT , SQL ISOPEN , SQL FOUND , and SQL NOTFOUND. Cursor FOR LOOP Statement.


With each iteration, the cursor FOR LOOP statement fetches a row from the result set into the record.

In each loop iteration, the cursor FOR LOOP statement fetches a row from the result set into its loop index. If there is no row to fetch, the cursor FOR LOOP closes the cursor. EXIT and GOTO, or raises an exception. An implicit cursor is a SQL statement that is contained within the executable section of the program and has an INTO statement (as in the case of a SELECT statement ). With an implicit cursor , Oracle will handle everything for you, but there is a cost to doing this: The program will run slower. The statement is not restricted as to the columns retrieved or number of tables joined.


Declaring the cursor defines the cursor with a name and the associated SELECT statement. You can, alternatively,. Opening the cursor allocates the memory for the cursor and makes it ready for fetching the rows returned by the SQL statement into it. There - in both cases - you meant to join. When I see SQL inside of a SQL loop - then you probably have a problem.


Since the BULK COLLECT fetches the record in BULK, the INTO clause should always contain a collection type variable. The article describes the Oracle cursors and their usage. There are two types of cursors - implicit and explicit cursor. Implicit cursor : Oracle automatically (implicit) controls or processes the information of SQL statement executed.


In this process, the user is unaware of implicit cursor. This context area is a memory region inside the Process Global Area (PGA).

Normally, the cursor is used when we need to process multiple rows of data. Oracle Engine uses a work area for its internal processing to execute SQL statements. The cursor is nothing but a pointer to this context area. The data stored in the cursor is called the active data set. To execute SQL statements, a work area is used by the Oracle engine for its internal processing and storing the information.


This work area is private to SQL’s operations. Select from a REF CURSOR - Oracle Server. Then you get to control all aspects: open, fetch, close.

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