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