To read more about ref cursor i have created a package to explain few different ref cursor examples. When you opt to use a weakly typed cursor, you can anchor it to a plsql structure that is a collection of a plsql record structure. When using the data provider to work with oracle ref cursors, you should consider the following behaviors. Actually, we have ref cursor as an out variable in the plsql procedure, hence trying to use it dynamically inside the cursor for loop conceptually wrong. I see no need for opening a ref cursor, dynamically or otherwise, so i would just use a regular cursor for loop. Cursor follows a defined execution cycle to execute the sql statement associated with it. Plsql ref cursor performance burleson oracle consulting. Ask tom difference between cursor and a ref cursor oracle. Cursor can be attached to only one query while ref cursor can be used to associate multiple queries at run time. Jun 23, 2011 the memory location to which it points is known as context area. Returning a ref cursor from a procedure plsql this example demonstrates how to define and open a ref cursor variable, and then pass it as a procedure parameter. How do i see the contents of the refcursor if i dont know the no of columns it is returning plsql thanks koshal.
Previous post we have explained detailed about different types of cursors. Different from implicit and explicit cursors, a cursor variable is not tied to any specific query. Declare type empcurtyp is ref cursor return emp%rowtype. You can open a ref cursor, dynamically or not, and fetch from it within a loop. Description this function takes an opened, parsed, and executed cursor and transformsmigrates it into a plsql manageable ref cursor a weaklytyped cursor that can be consumed by plsql native dynamic sqlswitched to use native dynamic sql. The openforusing statement associates a cursor variable with a query, executes the query, identifies the result set, positions the cursor before the first row in the result set, then zeroes the rowsprocessed count kept by %rowcount.
Now we create a print procedure that receives a ref cursor and prints the row data create or. Oracle cursor examples oracle plsql technology blog. Review the certification matrix for this product here. Two out ref cursors fetches around 70,000 records and for each record again some internal procedures gets called we have done some changes to queries used to fetch these ref cursors data. A ref cursor that specifies a specific return type. I am working on a system where oracle 11g is the back end database. There are two types of cursor variable 1week ref cursor. A cursor variable is like a c or pascal pointer, which holds the address of an item instead of the item itself.
A cursor variable is a variable that references to a cursor. I hope before knowing about ref cursors you would have a fair idea of what cursors in general are. What im trying to do is grab the info from the first cursor, select a few fields out of it and join to some other info and stick the result into a table variable. How do i see the contents of the refcursor if i dont know the no of columns it is returning. Now we want to use this ref cursor variable in our procedure, but we dont know the record structure. Returning a ref cursor from a oracle function stack overflow. Here is an example script that performs dynamic sql and returns the data as a ref cursor. Tuning dynamic sql with execute immediate statement and cursor variables. Cursor expressions as arguments to functions called from sql. You can describe the query, fetch from it, get the ith column, etc.
In essence, a ref cursor allows you to store the result of a bulk collect from a table or any pl sql cursor return set into a pl sql table ram array and then reference the array with the ref cursor as a pointer. Net type for the ref cursor type this section discusses the following aspects of using the ref cursor data type and oraclerefcursor objects obtaining an oraclerefcursor object. Download and unzip both files to the same directory. An oraclerefcursor object represents an oracle ref cursor. Net framework data provider for oracle supports the oracle ref cursor data type. I have a ref cursor defined as an out parameter and i am trying to get a receiving plsql to accept the ref cursor. Strongly typed the ref cursor type is restricted to an individual return type using the return clause. As other answers pointed out they are memory structures used to temporarily store and iterate through a query result set in plsql. Ask tom how do i see the contents of the refcursor if i.
The primary advantage of using cursor variables is their capability to pass result sets between sub programs like stored procedures, functions. Ask tom refcursors vs pipelined functions 11g oracle. A variable created based on such a data type is generally called a cursor variable. It represents a cursor or a result set in oracle database.
To create a cursor variable, define a ref cursor type, and then declare the cursor variable to be of that type. Oracle provides the for update clause of the select statement in an updatable cursor to perform this kind of locking mechanism. Determining whether to use plsql native compilation. Free oracle magazine subscriptions and oracle white papers. Plsql ref cursor and oraclerefcursor oracle help center. A ref cursor is a variable, defined as a cursor type, which will point to, or reference a cursor result. We will explain different types of cursors with simple examples. Stack overflow for teams is a private, secure spot for you and your coworkers to find and share information. Installation guides and general oracle database 11g documentation are here. Can you show an example of a ref cursor with dynamic sql. Using ref cursors 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 plsql data type whose value is the memory address of a query work area on the database. Ask tom how do i see the contents of the refcursor if i d. Plsql cursor variables with ref cursor oracle tutorial.
Or you can use a regular cursor for loop, which implicitly opens a cursor, not a ref cursor. Developers and dbas get help from oracle experts on. Using ref cursors 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 plsql data type whose value is the memory address of a query work area on the database. Declaring a cursor variable creates a pointer, not an item. In this case, oracle will close the cursor as soon as it is out of scope. Sometimes, you want to lock a set of rows before you can update them in your program. In essence, a ref cursor allows you to store the result of a bulk collect from a table or any plsql cursor return set into a plsql table ram array and then reference the array with the ref cursor as a pointer.
This section discusses the following aspects of using the ref cursor data type and oraclerefcursor objects. Using ref cursor s is one of the most powerful, flexible, and scalable ways to return query results from an oracle database. Ask tom fetch ref cursor to another ref cursor oracle. Using plsql stored procedures and ref cursors oracle docs. Cursor variables are defined using a ref cursor type. The memory location to which it points is known as context area. We can allocate different storage locations to the cursor when the program runs. This is known as an associative array, and commonly called a plsql table by folks who predate the oraclei documentation that oracle would prefer we forget. Can i see some examples of working ref cursor examples, especially passing a ref cursor between two programs. The advantage that a ref cursor has over a plain cursor is that is can be passed as a variable to a procedure or a function. On connection pools, cursor differentiation, and optimal. Example 711 procedure vulnerable to sql injection through data type. Although this reduces the chances of runtime errors. How to fetch data from the refcursor oracle community.
Dynamic sql with ref cursor burleson oracle consulting. The article describes the oracle cursors and their usage. I cant close ref cusor becasue of losing my result set. A ref cursor being a pointer to an open cursor used to send an open cursor as an out argument to the client app to loop through the record. The oracle ref cursor is a pointer data types that allows you to quickly reference any cursor result usually an internal plsql table array with data values kept in superfast ram. In essence, a ref cursor is a pointer or a handle to a result set on the database. Im trying to return two ref cursors from a procedure and having a bit of trouble. Weve got a function that, based on dynamically generated query, returns a ref cursor variable. Dynamic ref cursor with dynamic fetch an 11g version sometimes there is a problem as follows. In case you want to read the previous post oracle cursor basics all examples are tested in oracle 11g release 2 version. Doing a cursor loop fetch and inside doing another cursor loop fetch, is called a nested loop join and sql is significantly better and faster at. A ref cursor is a variable, defined as a cursor type. However, it fails if the resulting string is longer than 32k. Hence you close a ref cursor after you fetch from it.
You cannot define the same cursor more than stead you can only use it. For details, see the book plsql tuning with many oracle ref cursor examples and ref cursor tips. How cursor variables are defined is the topic of the next section. Application development tools such as oracle forms, which have a plsql engine, can use cursor variables entirely on the client side. Oraclerefcursor static methods are listed in table 1128. This example demonstrates how to define and open a ref cursor variable, and then pass it as a procedure parameter. The ref cursor is a data type in the oracle plsql language.
I need some inputs on since procedures returns control back when both these cursors sqls gets executed holding around 70,000 records. First, a ref cursor can be dynamically opened and defined at runtime, in contrast to a regular cursor, which is static and defined at compile time. Defining cursor variables ref cursor return clause. Oracle database 11g release 2 for microsoft windows x64. If you lose your result set that indicates you are not done with the ref cursor. Visit plsql challenge to read a complete explanation of the answers to this quiz. Meaning that a cursor variable can be opened for any query. This needs to be done using only sql and via a sql join, exists or in operation. The cursor variable is specified as an in out parameter so that the result set is made available to the caller of the procedure. For more information, see building a dynamic query with dynamic sql because this statement can use bind variables to make the sql. Pl sql ref cursor performance burleson oracle consulting. Dec 20, 2016 i hope before knowing about ref cursors you would have a fair idea of what cursors in general are. Using plsql stored procedures and ref cursors oracle.
Is it possible to have a plsql procedure that has dynamic sql and uses a ref cursor. Another difference is a cursor can be global a ref cursor cannot you cannot define them outside of a procedure function another difference is a ref cursor can be passed from subroutine to subroutine a cursor cannot be. Listing 1 creates a ref cursor and a regular cursor. Here is the syntax for declaring an updatable cursor. Ref cursor in oracle forms solutions experts exchange. However, it seems politically insensitive to use that language even though oracle published it as such. What is the difference between a normal cursor and a ref. A cursor variable can be associated with different queries at runtime.