This example executes a pl sql stored procedure that returns two ref cursor parameters, and reads the values using an oracledatareader. Creating a plsql stored procedure that uses ref cursors. However, i recognize that this may be just a simplification of your actual problem, which may require such things. The ref cursor can be assigned to other ref cursor variables.
An explicit cursor may accept a list of parameters. In oracle, cursor variables exist in the form of ref cursors that is, reference to a. The connection used to execute the command returning an oraclerefcursor object is. Oracle creates context area for processing an sql statement which contains all information about the statement. Thats it for this tutorial on the introduction to plsql ref cursors in oracle database. 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 must declare an explicit cursor for queries that return more than one row.
Mostly it is used as a generic cursor which can be passed as an argument to a stored sub program. Note that the sql projection of the cursor is unknown at compilation time. 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. A cursor variable is a variable that references to a cursor. Plsql and provide brief examples illustrating the important facets of the language. The primary advantage of using cursor variables is their capability to pass result sets between sub.
We could also rewrite the ref cursor example to use inparameter. Ask tom how do i see the contents of the refcursor if i. Returning a ref cursor from a procedure pl sql this example demonstrates how to define and open a ref cursor variable, and then pass it as a procedure parameter. Prior to oracle release 12c, result sets of sql queries were returned explicitly from the stored plsql subprograms via ref cursor out parameters. You need to have a sound understanding of sql and plsql basics. A weak ref cursor and a normal cursor may work differently but id have thought oracle would provide some syntactic sugar to allow me to treat one as the other to be used in a for loop. It allows a user to pass this reference to the same cursor among all the programs that need access to the cursor. This bulk collect can be used in select statement to populate the records in bulk or in fetching the cursor in bulk. Ref cursors are user defined types which is used to process multiple records and also these cursors also internally used record by record process generally, when we are using static cursors plsql runtime engine bounds single select statement at a time to the active set area at compile time, whereas ref cursors plsql runtime engine executes number of select statement dynamically for the. Each time you open the cursor, you can pass different arguments to the cursor, which results in different result sets.
Different from implicit and explicit cursors, a cursor variable is not tied to any specific query. A sql server cursor is a set of tsql logic to loop over a predetermined number of rows one at a time. However, sometimes, you may want to process a data set on a row by row basis. Apr 29, 20 ref cursor is a data type in the oracle. To read more about ref cursor i have created a package to explain few different ref cursor examples. Until oracle has retrieved all the rows then by definition it does not have an accurate record of how many there are. If you want to access the values in sql plus sql dev, pass a refcursor variable. In most other ways they behave similar to normal cursors. I have created a package to explain few different ref cursor examples. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. The same basic example is shown below except, the output is generated by a local procedure. You may find various types declared as ref cursor in plsql code that was written before oracle 9i was released. The following shows an example of a strong ref cursor.
A cursor is a pointer that points to a result of a query. This example executes a plsql stored procedure that returns two ref cursor parameters, and reads the values using an oracledatareader. It was developed by oracle corporation in the early 90s to enhance the capabilities of sql. A weakref cursor and a normal cursor may work differently but id have thought oracle would provide some syntactic sugar to allow me to treat one as the other to be used in a for loop. So far in this series we have covered the concepts of strong as well as weak ref cursor. I hope before knowing about ref cursors you would have a fair idea of what cursors in general are.
This example executes a plsql stored procedure that returns two ref cursor parameters, and fills a dataset with the rows that are returned. In oracle, i have a table called wine and a stored procedure that outputs a cursor based on the wine table. How to use ref cursor example a ref cursor is basically a data type. A ref cursor is a pl sql data type whose value is the memory address of a query work area on the database.
For basic oracle concepts, see oracle9i database concepts. 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 can allow more flexibility than writing a pl sql function that returns an array as its completely up to the client how many rows to fetch and when to. See the book oracle builtin packages and the corresponding oracle plsql. See also commit in the oracle database sql reference.
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. The number and types of elements in the variablelist must match those of the selectlist. A cursor variable can be associated with different queries at runtime. It declares a weak ref cursor and that too without declaring the ref pointer type. Implicit cursors are generated automatically by oracle server when an sql statement occurs in the pl sql executable part explicit cursors are declared and defined by the user when an query which appears in a pl sql return multiple lines as a result. Ive created an html form where the user can enter any combination of three values to retrieve results from the wine table. This may be a dumb question, but ive never got my head round the strange tablecast. A ref cursor is a variable, defined as a cursor type, which will point to, or reference a cursor result.
The following shows the syntax of a declaring a cursor with parameters. 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. That said, if it cant be done then that is the answer. Using plsql stored procedures and ref cursors oracle. 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. I want to pass a cursor to a procedure as in parameter. The purpose for the cursor may be to update one row at a time or perform an administrative process such as sql server database backups in a sequential manner.
Oracle database tips by donald burlesonapril 18, 2015. In essence, a ref cursor is a pointer or a handle to a result set on the database. Implicit cursors are generated automatically by oracle server when an sql statement occurs in the plsql executable part explicit cursors are declared and defined by the user when an query which appears in a plsql return multiple lines as a result both implicit and explicit cursors have attributes. That is the number and type of the columns have to match though not th. Meaning that a cursor variable can be opened for any query. In stateful applications this could be used to page through results. This website uses cookies to improve your experience while you navigate through the website. If you want to access the values in sqlplus sql dev, pass a refcursor variable. A cursor holds the rows returned by the sql statement. This example executes a pl sql stored procedure that returns two ref cursor parameters, and fills a dataset with the rows that are returned. A sql server cursor is a set of t sql logic to loop over a predetermined number of rows one at a time. If you assign a cursor variable to them, you can use the print command to print the. Or you can use a regular cursor for loop, which implicitly opens a cursor, not a ref cursor. The example below uses a ref cursor to return a subset of the records in the emp table.
Sqlplus looked at the ref cursor and saw that it was an open cursor. Sys ref cursor is an oracle built in cursor variable. As we learnt in the introduction to the ref cursor that there are three types of pl sql ref cursor in oracle database. 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 pl sql data type whose value is the memory address of a query work area on the database. The set of rows the cursor holds is referred as active set. Since the bulk collect fetches the record in bulk, the into clause should always contain a collection type variable. Procedure that outputs a dynamic plsql cursor question. The ref cursor is a datatype in the oracle pl sql language. Whenever oracle executes an sql statement such as select into, insert, update, and delete, it automatically creates an implicit cursor. A cursor contains information on a select statement and the rows of data accessed.
This section discusses the following aspects of using the ref cursor datatype and oraclerefcursor objects. Plsql cursor variables with ref cursor oracle tutorial. Suggestions, comments, feedbacks and referrals are highly appreciated. Can i see some examples of working ref cursor examples, especially passing a ref cursor. It contains all information needed for processing the statement.
Once its fetched all the rows it closes the cursor. Other languages like proc, oci, jdbc, vb they can get a cursor and describe it. Ref cursor s are represented through the oraclerefcursor odp. This section discusses the following aspects of using the ref cursor data type and oraclerefcursor objects. Cursors with a defined return type are strongly typed. I see no need for opening a ref cursor, dynamically or otherwise, so i would just use a regular cursor for loop. Net type for the ref cursor type this section discusses the following aspects of using the ref cursor datatype and oraclerefcursor objects obtaining an oraclerefcursor object. Sql server cursor explained by examples sql server tutorial. A variable created based on such a data type is generally called a cursor variable. Oracle creates a memory area, known as context area, for processing an sql statement, which contains all information needed for processing the statement, for example, number of rows processed, etc.
One can use a ref cursor as target of an assignment, and it can be passed as parameter to other program units. Dec 20, 2016 i hope before knowing about ref cursors you would have a fair idea of what cursors in general are. Cursor expressions as arguments to functions called from sql. 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. On the screen, you can issue the following set command prior to the plsql block. The ref cursor is a data type in the oracle pl sql language. Description this function takes an opened, parsed, and executed cursor and transformsmigrates it into a pl sql manageable ref cursor a weaklytyped cursor that can be consumed by pl sql native dynamic sqlswitched to use native dynamic sql.
Oracle cursor examples oracle plsql technology blog. The data represented by the ref cursor is accessed in a forwardonly, serial manner. Oracle plsql by example benjamin rosenzweig, elena silvestrova rakhimov. When an sql statement is processed, oracle creates a memory area known as context area.
Plsql cursor by practical examples oracle tutorial. You cannot position a record pointer inside the ref cursor to point to random records in the result set. Plsql is one of three key programming languages embedded in the oracle database, along with sql itself and java. In oracle, dual is a table owned by the sys user, which has a single column, dummy. In plsql, a cursor is a name assigned to a specific private sql area for a specific. Oracle plsql ref cursors ref cursors a ref cursor or cursor variable is just a reference or a handle to a static cursor.
Introduction to plsql ref cursors in oracle database. 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. The plsql compiler will verify that the fetch clause has the correct. Oracle plsql provides the functionality of fetching the records in bulk rather than fetching onebyone. Plsql allows the programmer to control the context area through the cursor. 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. Apr 26, 2020 a cursor is a pointer to this context area. Oracle advanced plsql developer professional guide. Commandtype 4 adcmdstoredproc dim param1 set param1 cmd.
Pdf of oracle pl sql and cursor example sql sql create demo table sql create table employee 2 id varchar24 byte not null, 3 firstname varchar210 byte, 4 lastname. Hi vicky, plz check below example i am using emp table. Pl sql allows the programmer to control the context area through the cursor. Plsql is a combination of sql along with the procedural features of programming languages.
As other answers pointed out they are memory structures used to temporarily store and iterate through a query result set in plsql. The example below uses a ref cursor to return a subset of the records in the emp. See also the keyword cursor and ref cursors in plsql. Now i would like to retrieve more than one column or entire row of information using the same. A cursor holds the rows oneormore returned by a sql. The key difference is you can only assign queries that match the return type to a strong cursor. This example demonstrates how to define and open a ref cursor variable, and then pass it as a procedure parameter. A cursor is a pointer to a private sql area that stores information. The ref cursor is a datatype in the oracle plsql language. It represents a cursor or a result set in oracle database. In plsql, the context area is controlled by cursor. This is a powerful capability in that the cursor can.
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