Implicit cursors are managed by the oracle engine itself. Normal cursor is a static cursor in which the query is assigned at design time and cant be changed at run time. Another difference is a ref cursor can be returned to a client. Ref cursors may be dynamically opened or opened based on logic. There are some important differences between regular cursors and ref cursors which are following. To declare a cursor variable, you use the ref cursor is the data type. Db2 cannot use optimistic concurrency control for dynamic scrollable cursors. The db api definition does not allow for keyword parameters. Anchor the cursor statement to a table or view in the database catalog. In plsql what is a difference between a cursor and a. A ref cursor essentially encapsulates the results of a query. A cursor variable has datatype ref cursor, and you might see them referred to informally as ref cursors.
You cannot define the same cursor more than stead you can only use it. A ref cursor can be dynamically opened and is defined at runtime. Comparison operators cannot be used to test cursor variables for equality. Oracle generously provides a list of things developers can do to tune their plsql code. What is the difference between cursor and procedures. Differences between regular cursors and ref cursors dba. One item from that list is probably the single best tool developers have at their disposal to supercharge their code. The package specification defines what is contained in the package. Lets first check the basic example of cursor and ref cursors.
To define cursor variable, you must decide which ref cursor data type to use. Returning columns with datatype and length need to be known at compile time. A ref cursor, then, identifies a reference to a cursor variable. The output parameter with the oracledbtype property set is bound to oracledbtype. Postgresql provides us with a special type called refcursor to declare a. Create an array variable associated with the cursor of the given type and size and return a variable object. The following example includes a parameterized cursor. I would like to use ref cursors as parameters instead of string because they are much easer to transform into tables of records with fetch bulk collect into. A cursor variable is a variable of ref cursor data type which is a pointer to a data structure resource. Because many cursor variables might exist to point to many work areas, ref cursor can be thought of as a category or data type specifier that identifies many different types of cursor variables. An explicit cursor declared within the current scope. Scope of cursor variable is wider than explicit cursor, we can use cursor variables to pass query result sets between subprograms or pass a cursor variable as an argument to a procedure or function. Example 627, passing a ref cursor as a parameter example 629, stored procedure to open a ref cursor example 630, stored procedure to open ref cursors with different queries example 631, cursor variable with different return types related topics. A regular cursor must be directly addressed not passed and cannot be returned to a client application.
Create a record structure to store rows of the reference cursor in an ordinary fetch, or a record structure and associative array collection data type to store a set of rows of the reference cursor. An array declared in a plsql host environment and passed to plsql as a. Difference between implicit cursor and explicit cursor. A plsql cursor variable or parameter declared within the current scope.
One can use a ref cursor as target of an assignment, and it can be passed as parameter to other program units. The declare section of a plsql block and used within its executable section. Cursors with a defined return type are strongly typed. In this case, we declare a type to be a ref cursor, and use it as an out parameter in a stored procedure. Between fetch operations and subsequent positioned update or delete operations.
Count 268056 the difference between 267985 and 268056 isnt huge, but there is still a difference. Had history been different, and had the ref cursor and the cursor variable been introduced first and had the batched bulk fetch constructs been supported. Difference between explicit cursor and cursor variable. A ref cursor is a plsql data type whose value is the memory address of a. In short, the salient differences between regular cursors and ref cursors are as follows. What is the difference between a normal cursor and a ref. Onmouseover,call function but as cursor moves cursor changes whole time. So using a ref cursor gives us a lot more control over the final sql statement which gets executed. 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. If you want to access the values in sqlplus sql dev, pass a refcursor variable. The cursor displays the name and salary of each employee in the emp table whose salary is less than that specified by a passedin parameter value.
Some really nice aspects of cursor variables, demonstrated in this package. Stored functions have a single return value parameter. You cannot use a cursor variable where a cursor is expected, or vice versa. I didnt read the article, so im guessing here a little but to me cursor oriented means if i want to update a table i would declare a cursor in plsql or any language, open it, and then process each row i want to update, one row at a time, then close the cursor. The key difference is you can only assign queries that match the return type to a strong cursor. Ref cursors also provide the feature of passing parameters. Ref cursor types may be passed as parameters to or from stored procedures and functions. A cursor is really any sql statement that runs dml select, insert, update, delete on your database. There are two types of cursor variable 1week ref cursor. The developer does not explicitly declare the cursor, thus, known as implicit cursor. It connects to query statement result, similar to the cursor data type. That is the number and type of the columns have to match though not the column names. The cursor variable is specified as an in out parameter so that the result set is made available to the caller of the procedure.
Ref cursor is typically used to return record set or a cursor from stored procedure. The return type of a function may also be a ref cursor type. None of the output parameters of type oracledbtype. This provides the capability to modularize the operations on a cursor into separate programs by passing a cursor variable between programs. Plsql creates an implicit cursor whenever an sql statement is executed through the code, unless the code employs an explicit cursor. In essence, a ref cursor is a pointer or a handle to a result set on the database. Ref cursor is the oracle data type for a cursor variable.
Refcursor is populated after the executereader method is invoked if there are multiple output ref cursor parameters. A ref cursor is a datatype that holds a cursor value in the same way that a varchar2 variable will hold a string value a ref cursor can be opened on the server and passed to the client as a unit rather than fetching one row at a time. However, explicit cursor scope is limited to that plsql block only. Cursor parameters can appear in any part of the declare cursor. The ref cursor and the cursor variable were introduced into plsql later than the explicit cursor to overcome the latters restrictions. Explicit cursors are the cursors created by the user inside a plsql block. Rows are read with a fetch statement before the cursor is finally closed with a close. Structured does not need to be known at compile time. Hi, when i learning about cursor variable ref cursor on one website i found this code. What is plsql plsql anonymous block plsql data types plsql variables plsql comments. Following example shows how does ref cursor can be used to call subprogram. My dev person says that he cannot construct a ref cursor in weblogic java so that he can pass it to me.
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 cursor variables with ref cursor oracle tutorial. The other difference is that, because a ref cursor is a pointer it can be passed between programs. 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.
What is the difference between a normal cursor and a ref cursor. Parameterized cursors are static cursors that can accept passedin parameter values when they are opened. Unlike an explicit cursor, which always refers to the same query work area, a cursor variable can refer to different work areas. On connection pools, cursor differentiation, and optimal. A ref cursor data type can be obtained as an oracledatareader object by calling the executereader method of the oraclecommand object. This is very useful for passing data from plsql to other languages, for instance a jdbc result set. A ref cursor can be passed to another plsql routine or returned to a client. The comparison value for col1 is inserted via a using parameter, so it needs no. Edb postgres jdbc connector edb postgres language pack edb postgres. Difference between cursor and ref cursor oracle database. With dynamic scrollable cursors, the most recently fetched row or page from the base table remains locked to maintain position for a positioned update or delete. These examples reference the following stored procedure definition. A more interesting usage is to return a reference to a cursor that a function. In stateful applications this could be used to page through results.
1527 911 1292 967 264 869 1125 848 247 1080 772 312 1533 222 364 304 214 464 256 1254 1358 1069 1290 490 377 647 1104 322 113 765 303 18 1508 658 1053 1406 1216 310 915 1238 763 161 1292 1178 1149