In general, yes you can, you just nest another execution block inside your current one... begin declare cursor x is select dummy from dual; begin... end ; end ; / BluShadow Member, Moderator Posts: 42,305 Red Diamond Nov 6, 2008 6:42AM However if you just want to pass a value as a parameter to a cursor you can do...
How does declare cursor work?
Here is how it works: The first important thing to notice is that a cursor can only be declared inside a transaction. However, there is more: The second important this is that DECLARE CURSOR itself is lightning fast. It does not calculate the data yet but only prepares the query so that your data can be created when you call FETCH.
Can I use a Cursor FOR loop instead of explicit cursor?
But you could use a cursor for loop instead of declaring an explicit cursor. But anyway, this would be slower as row-by-row is slow-by-slow.
What to do when the cursor does not find a row?
In MySQL, you need to declare a variable to handle the situation when the cursor does not find a row. This is called a Not Found Handler, and it’s done using the line starting with DECLARE CONTINUE HANDLER. It says when there are no records found, set the done variable (which we declared earlier) to true. Open the cursor.
Can you declare multiple cursors in the same PL/SQL block?
You can declare multiple cursors in the same pl/sql block. There is no need to declare the second cursor after you've opened the first cursor!
Can we use cursor in begin block?
In general, yes you can, you just nest another execution block inside your current one... However if you just want to pass a value as a parameter to a cursor you can do...
How do you create a cursor in start block?
Before using an explicit cursor, you must declare it in the declaration section of a block or package as follows:CURSOR cursor_name IS query;OPEN cursor_name;FETCH cursor_name INTO variable_list;CLOSE cursor_name;cursor_name%attribute.More items...
Where do we declare cursor?
A cursor declared with the SCROLL option must be left positioned before the first row before exiting from the stored procedure. The cursor is declared with the WITH HOLD option if the stored procedure is defined to commit on return.
Can we declare variable in begin block in PL SQL?
You can declare constants and variables in the declarative part of any PL/SQL block, subprogram, or package. Declarations allocate storage for a value, specify its datatype, and specify a name that you can reference. Declarations can also assign an initial value and impose the NOT NULL constraint.
Can we have two cursors in a procedure Oracle?
The trick to declaring a cursor within a cursor is that you need to continue to open and close the second cursor each time a new record is retrieved from the first cursor. That way, the second cursor will use the new variable values from the first cursor.
Can we pass cursor as parameter?
No, you can't pass a static cursor as a parameter.
Where do we declare cursor in COBOL?
In COBOL source programs, a DECLARE CURSOR command is checked to verify whether host variables exist in either the LINKAGE or WORKING STORAGE section. In COBOL applications (as mentioned above), an application called from another application cannot use a cursor that was declared by the calling application.
Can we declare cursor in procedure division?
hi , actually u can declare cursor in procedure division or working storage section.
Is declare cursor executable?
It is not an executable statement and cannot be dynamically prepared.
Can we declare same variable inside the inner and outer block?
Outer block can't access variables declared inside Inner Block. Question 4 Explanation: If same variable is declared inside inner as well as outer block then higher priority will be given to inner block.
Can we call the function in anonymous block?
The declaration of the function should be always at the end of the declare section of an anonymous block after all the necessary declarations of the anonymous block are declared....PL/SQL declare function within an anonymous block.Line no.Description8Start of the declare section of the function.9Start of the execution section of the function.15 more rows
Which of the option is incorrect for declaring a variable?
4. Which of the following is not a valid variable name declaration? Explanation: Variable name cannot start with a digit.
How do you declare a variable in cursor?
A cursor variable is like an explicit cursor that is not limited to one query. To create a cursor variable, either declare a variable of the predefined type SYS_REFCURSOR or define a REF CURSOR type and then declare a variable of that type. You cannot use a cursor variable in a cursor FOR LOOP statement.
Where is cursor stored in SQL Server?
SQL Server static cursors are always read-only. Because the result set of a static cursor is stored in a worktable in tempdb, the size of the rows in the result set cannot exceed the maximum row size for a SQL Server table.
How do you define cursor?
1) A cursor is the position indicator on a computer display screen where a user can enter text. In an operating system with a graphical user interface (GUI), the cursor is also a visible and moving pointer that the user controls with a mouse, touch pad, or similar input device.
What happens when a cursor is declared?
Was this helpful? The DECLARE CURSOR statement associates a cursor name with a SELECT statement (as described in SELECT (Interactive)). Assigns a name to the cursor. The name can be specified using a quoted or unquoted string literal or a host language string variable.
Best Answer
In general, yes you can, you just nest another execution block inside your current one...
Answers
In general, yes you can, you just nest another execution block inside your current one...
Can you use join instead of pl_sql?
Avoid nested loops for updates. In most cases you can use join instead of nested pl_sql loops. Also consider bulk/forall.
Can you use input parameters in cursor?
It sounds like you are using cursor with input parameters - you can pass input values into cursor same way as into procedure and use them inside cursor as binds.
What is an explicit cursor?
An explicit cursor is one that is declared by the PL/SQL code. You have more control over it and how the data is handled.
What is a cursor in a database?
However, many database vendors include the ability to process rows individually. This is what a cursor does. Cursors allow you to store a result set in a variable, and loop through it to perform logic and actions on each row.
Why do we use a cursor in SQL?
Using a cursor in SQL to iterate through a set of data to perform logic often has performance issues. It goes against how data sets work in SQL. Normally, SQL cursors should be avoided. Most of the time, when code is written using an SQL cursor, it is:
How many types of cursors does Oracle have?
Oracle actually has two different types of cursors: implicit cursors and explicit cursors.
What does the close step do in a fetch?
Finally, once all of the results have been processed and the Fetch stage is finished, the Close step will release the cursor from memory and allow you to continue with the application.
How many steps are there in the lifecycle of a cursor?
There are four steps in the lifecycle of a cursor:
Is using a cursor bad?
Cursors aren’t bad, generally. But they are often misused by many developers, causing them to perform a task much slower than using alternative methods such as plain SQL.
What is the simplest cursor?
Declaring a cursor without any parameters is the simplest cursor. Let's take a closer look.
What is a cursor in PLSQL?
A cursor is a SELECT statement that is defined within the declaration section of your PLSQL code. We'll take a look at three different syntaxes to declare a cursor.
Can you declare a cursor with a return clause?
Finally, we can declare a cursor with a return clause.
Can you declare cursors with parameters?
As we get more complicated, we can declare cursors with parameters.
When are implicit cursors used in SQL?
It holds the affected rows by the DML operations like UPDATE, DELETE and INSERT. Thus implicit cursors are used when we don’t have an explicit cursor in place.
How to run a cursor in Oracle?
Answer: To run a cursor in Oracle, the syntax is: OPEN <<CURSORNAME>>. The CURSORNAME refers to the name of the cursor available in the declaration section of the PL/SQL block of code.
What is the memory called after a SQL statement is executed?
Answer: After an SQL statement is executed, the Oracle database builds a memory called context area . A cursor has the information processed from a select statement and contains the rows updated by that SELECT operation.
What is a cursor in PL/SQL?
A cursor in PL/SQL gives a name and acts as a pointer to the area of work called a context area and then uses its information. It keeps the number of rows processed by the SQL statement. These rows are called as an active set. The size of the active set is equal to the count of the rows that meet the condition.
What is cursor variable?
A cursor variable is used to refer to the present row in the result set that has more than one row. It can be used for any type of query. It is similar to a variable of PL/SQL, where we can assign values and can be passed via a subprogram in the database.
What is the start of a substring?
Finds the substring i in x string and then returns the position of occurrence. The start refers to the beginning position of searching and is an optional parameter. The n is the nth occurrence of the string and is also an optional parameter.
Can you use a cursor for loop?
Cursor FOR Loop has the loop index as a record which points to the row obtained from the database. Next after opening the cursor, it fetches the multiple rows of data repeatedly from the result set into the record fields.
Why does PostgreSQL not return?
There is a reason for that: PostgreSQL will send the data to the client and the client will return as soon as ALL the data has been received. If you happen to select a couple thousand rows, life is good, and everything will be just fine.
Why does PostgreSQL go for a sequential scan?
If the entire resultset is fetched, PostgreSQL will go for a sequential scan and sort the data because the index scan is considered to be too expensive:
What is the default value of PostgreSQL?
The default value is 0.1 , which means that PostgreSQL optimizes for the first 10%. The parameter can be changed easily in postgresql.conf just for your current session.
Can a cursor be declared?
The first important thing to notice is that a cursor can only be declared inside a transaction. However, there is more: The second important this is that DECLARE CURSOR itself is lightning fast. It does not calculate the data yet but only prepares the query so that your data can be created when you call FETCH.
Do you use keyset pagination in application code?
Of course you'd use keyset pagination in application code - where else ?
Does PostgreSQL use cursors?
Cursors are treated by the optimizer in a special way. If you are running a “normal” statement PostgreSQL will optimize for total runtime. It will assume that you really want all the data and optimize accordingly. However, in case of a cursor it assumes that only a fraction of the data will actually be consumed by the client. The following example shows, how this works:
