Sql procedure loop while updating records using cursors
Best of all, Oracle Database automatically optimizes cursor FOR loops to perform similarly to BULK COLLECT queries (covered in “Bulk Processing with BULK COLLECT and FORALL,” in the September/October 2012 issue of ).So even though your code looks as if you are fetching one row at a time, Oracle Database will actually fetch 100 rows at a time—and enable you to work with each row individually.
In the online version (which also matches the quiz offered at PL/SQL Challenge, both a and b are correct.
Visit PL/SQL Challenge to read a complete explanation of the answers to this quiz. If the SELECT statement identifies more than one row to be fetched, Oracle Database will raise the TOO_MANY_ROWS exception.
DECLARE @start SMALLDATETIME = '2015-08-06T'; ; WITH x AS ( SELECT id, creatie, rn = ROW_NUMBER() OVER (ORDER BY id) - 1 FROM dbo.
There can be a situation where you have to use a cursor, even though the experts say not to use cursors or to avoid them as much as possible.
Table 1: Possible error messages if INTO and SELECT lists do not match A SELECT-INTO is also referred to as an implicit query, because Oracle Database implicitly opens a cursor for the SELECT statement, fetches the row, and then closes the cursor when it finishes doing that (or when an exception is raised).
You can, alternatively, explicitly declare a cursor and then perform the open, fetch, and close operations yourself.With a cursor FOR loop, the body of the loop is executed for each row returned by the query.The following block uses a cursor FOR loop to display the last names of all employees in department 10: DECLARE CURSOR employees_in_10_cur IS SELECT * FROM employees WHERE department_id = 10; BEGIN FOR employee_rec IN employees_in_10_cur LOOP DBMS_OUTPUT.put_line ( employee_rec.last_name); END LOOP; END; The nice thing about the cursor FOR loop is that Oracle Database opens the cursor, declares a record by using %ROWTYPE against the cursor, fetches each row into a record, and then closes the loop when all the rows have been fetched (or the loop terminates for any other reason).But if you look closely, most of the time we use cursors to iterate through a row collection and update the same table.In these type of situations, it is ideal to use a Update Cursor, than using the default read only one.If the statement doesn’t identify any rows to be fetched, Oracle Database will raise the NO_DATA_FOUND exception.Here are some examples of using SELECT-INTO: Get the last name for a specific employee ID (the primary key in the employees table): If there is a row in the employees table with ID 138, this block will display the last name of that employee.A cursor is a pointer to a private SQL area that stores information about the processing of a SELECT or data manipulation language (DML) statement (INSERT, UPDATE, DELETE, or MERGE).Cursor management of DML statements is handled by Oracle Database, but PL/SQL offers several ways to define and manipulate cursors to execute SELECT statements.The syntax of this statement is The PL/SQL Challenge question in last issue’s “Wrap Up Your Code in a Neat Package” article focused on how the values assigned to package-level variables persist in your session and asked, “Which of the choices will display ‘3’ after execution?” In the print version of the article, only choice a was correct.