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. Although this reduces the chances of runtime errors. This form of expression is equivalent to the plsql ref cursor and can be passed as a ref cursor argument to a function. A quick introduction to oracle ref cursors using oracle application express. I could not understand the technical terms of below paragraph in a clientserver environment, for example, a program on the client side could open and start fetching from the cursor variable, and then pass that variable as an argument to a stored procedure on the server.
Meaning that a cursor variable can be opened for any query. Oracle creates context area for processing an sql statement which contains all information about the statement. Sqlplus looked at the ref cursor and saw that it was an open cursor. A cursor variable can be associated with different queries at runtime. 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. This example demonstrates how to define and open a ref cursor variable, and then pass it as a procedure parameter. I wrote a stored procedure using ref cursor,and be a data set of reporting service. Cursor in, cursor out oracle magazine oracle blogs. 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.
This scenario can be explained using a simple example shown below. You must, of course, use the sql language to access tables, and each time you do so, you use a cursor to get the job done. Learn what are cursors, what are typesexplicit and implicit, and steps of cursors creation in oracle database by manish sharma from. Different types of cursors in plsql oracle live sql. Determining whether to use plsql native compilation. Dec 20, 2016 i hope before knowing about ref cursors you would have a fair idea of what cursors in general are. The primary advantage of using cursor variables is their capability to pass result sets between sub programs like stored procedures, functions. Creating a plsql stored procedure that uses ref cursors. We will explain different types of cursors with simple examples. In essence, a ref cursor is a pointer or a handle to a result set on the database. Using pipelined and parallel table functions oracle. By using ref cursor we can change the select statement dynamically at runtime which is available in the cursor definition based on some validation.
Ref cursor in oracle forms solutions experts exchange. Mar 27, 2005 i have just opened the ref cursor with one sql here for this example but it is built dynamically based on the input values. Free oracle magazine subscriptions and oracle white papers. I cant close ref cusor becasue of losing my result set. Two cursor variables were created over a single refcursor type declared in the package specification. This book includes scripts and tools to hypercharge oracle 11g performance and you can buy it for 30% off directly from the. A ref cursor is a variable, defined as a cursor type, which will point to, or reference a cursor result. Different behavior for ref cursor between oracle 10g and. 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. Last issue, i wrote about some new oracle database 11g features, and i continue that coverage in this issue, focusing on my favorite procedural language, plsql. The cursor variable is specified as an in out parameter so that the result set is made available to the caller of the procedure. You create and return a ref cursor inside a plsql code block.
To read more about ref cursor i have created a package to explain few different ref cursor examples. 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. A cursor holds the rows returned by the sql statement. A cursor variable is a pointer that distinguishes the current row in a resultset from a multirow query. Note that if you use only for update clause and do not include one or more column after the of keyword, oracle will then lock all selected rows across all tables listed in the from clause. How cursor variables are defined is the topic of the next section. I used the classic dept and emp tables to illustrate. Oracle cursor examples oracle plsql technology blog.
Whenever oracle executes an sql statement such as select into, insert, update, and delete, it automatically creates an implicit cursor. This stored program could then continue fetching and pass control back to the client. Introduction to oracle 11g cursors eye on databases. Plsql cursor variables with ref cursor oracle tutorial. A ref cursor is a variable, defined as a cursor type. When cursor result set contains multiple records, it has to be iterated to fetch each of them. Showing equipment records by using a ref cursor oracle docs. As other answers pointed out they are memory structures used to temporarily store and iterate through a query result set in plsql. In contrast, explicit cursors are tied to individual queries. The example below uses a ref cursor to return a subset of the records in the emp table. Plsql ref cursor performance burleson oracle consulting.
I have very limited permissions on the database and as such all i can do is call procedures that reside in packages. Strong plsql ref cursors burleson oracle consulting. Developers and dbas get help from oracle experts on. The plsql package defines the ref cursor and contains the definition of the stored. Ask tom difference between cursor and a ref cursor oracle. The refcursor declared in this programs scope is never opened as when it is assigned to the same refcursors variable in the out parameter, the information of the cursor variable from the server program is copied into this variable, thus making it its alias. Simple grid report example using basic oracle stored procedure in japser design studio 6.
For example, suppose that you want a function to read a set of external files in parallel and return the records they contain. A ref cursor is a plsql data type whose value is the memory address of a query work area on the database. Posted in oracle, plsql cursor example oracle cursor example oracle cursor examples published by sqlandplsql to learn more about the oracle, sql, pl sql, performance tuning, database modeling, ubuntu, mysql etc. I have just opened the ref cursor with one sql here for this example but it is built dynamically based on the input values.
Ref cursor to bulk fetch all column values along with rowids. Basically, the procedure opens a reference cursor, updates a table then completes. A cursor is a pointer to a private sql area that stores information. Hi tom, feels good that i got a chance to ask you a question. Opviiously the parameter for open cursor should be varchar2 which wil not accept 32767 characters event resultant of concatenation operator should be varchar2 may be you need to try to execute ur query in parts. Strong plsql ref cursors oracle plsql tips by boobal ganesan.
Our technologist takes another look at oracle database 11g. Part 12 in a series of articles on understanding and using plsql. Even though the example cursor variable is defined, the record can not use it because the cursor variable return type is not defined. Different from implicit and explicit cursors, a cursor variable is not tied to any specific query. Tuning dynamic sql with execute immediate statement and cursor variables. To use parallel execution with a leaflevel table functionthat is, a function to perform a unitary operation that does not involve a ref cursorarrange things so as to create a need for a ref cursor. 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. The set of rows the cursor holds is referred as active set. Different behavior for ref cursor between oracle 10g and 11g. I shall rewrite the cursor in example code 5 for loop as below. A normal loop is used to iterate the result set and display the results.
A nested cursor is implicitly opened when the cursor expression is evaluated. Cursor variables are defined using a ref cursor type. I hope before knowing about ref cursors you would have a fair idea of what cursors in general are. Previous post we have explained detailed about different types of cursors. It has worked consistently until the upgrade to oracle 11g. A cursor is a pointer that points to a result of a query. I have a ref cursor defined as an out parameter and i am trying to get a receiving plsql to accept the ref cursor. Jun 23, 2011 cursor for loops, as illustrated above, can be extended to include subqueries as dynamic cursors. Oracle magazine subscriptions and oracle white papers. Resultset 5 in the query editor manually type the field names and provide types to them as shown in below image.
Strongly typed the ref cursor type is restricted to an individual return type using the return clause. Cursor variables have several advantages over explicit cursors including. 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. The central purpose of the oracle plsql language is to make it as easy and efficient as possible to query and change the contents of tables in a database. Cursor variables can point to a variety of queries provided the queries have a suitable return type. Can i see some examples of working ref cursor examples, especially passing a ref cursor between two programs. I thought i might be able to try something like this. As such it went into a loop, fetching each row of data from the database, using the ref cursor as its reference pointer to the relevant query, and displaying each row of data until it had no more rows to fetch. For example, suppose that you want a function to read a set of. From a different procedure, i want to use this return value in some record so i want to declare a cursor. In 10g the cursor will contain the expected results but in 11g the cursor will be empty. Cursor can be attached to only one query while ref cursor can be used to associate multiple queries at run time. If you lose your result set that indicates you are not done with the ref cursor.
Oracle pl sql interview question explain ref cursor strongly typed ref. Declare type empcurtyp is ref cursor return emp%rowtype. Plsql cursor by practical examples oracle tutorial. A ref cursor that specifies a specific return type. It represents a cursor or a result set in oracle database. For example, if a dataset is populated by executing a stored procedure that. For this we need to define ref cursor type by using following syntax. This variable is then looped for processing the returned result set as shown in. In case you want to read the previous post oracle cursor basics all examples are tested in oracle 11g release 2 version. The ref cursor is a data type in the oracle plsql language. A cursor can allow more flexibility than writing a plsql function that returns an array as its completely up to the client how many rows to fetch and when to. Plsql ref cursor and oraclerefcursor oracle help center.
Using plsql stored procedures and ref cursors oracle docs. Once you load a plsql table an inram array, a ref cursor allows you to reference. Jun 29, 2016 i am working on a system where oracle 11g is the back end database. Net framework data provider for oracle supports the oracle ref cursor data type. Oct 23, 2012 opviiously the parameter for open cursor should be varchar2 which wil not accept 32767 characters event resultant of concatenation operator should be varchar2 may be you need to try to execute ur query in parts. Defining cursor variables ref cursor return clause. Plsql allows the programmer to control the context area through the cursor. Suggestions, comments, feedbacks and referrals are highly appreciated. There he asked one question as what is the difference between cursor and ref cursor, and when would you appropriately use each of these. Using plsql stored procedures and ref cursors oracle. A variable created based on such a data type is generally called a cursor variable. In this case, oracle only locks rows of the table that has the column name listed in the for update of clause. Oracle database tips by donald burlesonapril 18, 2015.
This implies that the cursors would not be declared in the declare section, but would be implicitly created when a subquery is attached to the for loop. Net as a returnvalue parameter, without using a stored function or procedure. In stateful applications this could be used to page through results. A cursor variable is a variable that references to a cursor. The plsql code below declares a cursor which selects employee details from department 10. Simple grid report example using basic oracle stored.
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