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Updating specific row in cursor

In computer science, a database cursor is a control structure that enables traversal over the records in a database.Cursors facilitate subsequent processing in conjunction with the traversal, such as retrieval, addition and removal of database records.You cannot specify multiple collations for an operation.For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort.

You cannot have an array filter document for an identifier if the identifier is not included in the update document.

The database cursor characteristic of traversal makes cursors akin to the programming language concept of iterator.

Cursors are used by database programmers to process individual rows returned by database system queries.

With a non-scrollable (or forward-only) cursor, you can each row at most once, and the cursor automatically moves to the next row.

After you fetch the last row, if you fetch again, you will put the cursor after the last row and get the following code: SQLSTATE 02000 (SQLCODE 100).

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  1. The SELECT statement associated with the cursor does not have any locks on the rows it returns, allowing any session to perform any operation on those rows during the cursor operation. When we want to issue a lock over the record set returned by the cursor associated SELECT query, we can opt for the FOR UPDATE.

  2. The reason some of your rows are getting NULLs updated is due to the subquery. When the subquery fails to find a matching row in tblB, the subquery returns NULL. But since the UPDATE has no WHERE clause, it will update all rows, even those where the subquery returns NULL.

  3. A cursor is a pointer to a specific row in ResultSet. In Java applications, all ResultSets are cursors. A cursor is updatable; that is, you can update or delete rows as you step through the ResultSet if the SELECT statement that generated it and its underlying query meet cursor updatability requirements, as detailed below.

  4. Set feedback off create table f a number, b varchar210; insert into f values 5,'five'; insert into f values 6,'six'; insert into f values 7,'seven'; insert into f values 8,'eight'; insert into f values 9,'nine'; commit; create or replace procedure wco as cursor c_f is select a,b from f where lengthb = 5 for update; v_a f.a%type; v_b.

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