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