News: ref cursor with bulk collect example in oracle

COMMIT makes permanent any database changes made during the current transaction. Whether you issue the commit or rollback in your PL/SQL program or from a client program depends on the application logic. Example 6-17 uses %ROWCOUNT to test if more than ten rows have been fetched. Excuse me, can the applet monitor who sent the applet code? For full control over query processing, you can use explicit cursors in combination with the OPEN, FETCH, and CLOSE statements. Because the fetched rows are not locked by a FOR UPDATE clause, other users might unintentionally overwrite your changes. Select the rowid of each row into a UROWID variable, then use the rowid to identify the current row during subsequent updates and deletes. The BULK COLLECT clause lets you fetch all rows from the result set at once. Array of records can be converted to cursor by using TABLE CAST as shown in example. Used with ROLLBACK, SAVEPOINT undoes part of a transaction. Example 6-27 defines a REF CURSOR type, then declares a cursor variable of that type as a formal parameter. You specify the direction in which the query traverses the tree (down from the root or up from the branches) with the PRIOR operator. The number of active savepoints for each session is unlimited. Without a cursor variable, you have to fetch all data from a cursor, store it in a variable e.g., a collection, and pass this variable as an argument. Be careful not to cause set subscripts to cross bounds because index_row. See "Overview of Transaction Processing in PL/SQL". PL/SQL creates a record variable with fields corresponding to the columns of the result set. In that case, you must make sure the row is not changed by another user before the update.

PRIOR refers to the parent row of the current row returned by a tree-structured query. PL SQL basically stands for "Procedural Language... What is For Loop? When using FORALL, the following rules should be followed: Description: Using BULK COLLECT, all rows can be extracted at one time and bound to record variables, which is called batch binding. Use bound variables. However, this size limit can be easily achieved by introducing the ROWNUM condition in the 'SELECT' statement, whereas in the case of cursor this is not possible. SELECT local_type(empno, ename) BULK COLLECT INTO l_recs. If the statement fails, Oracle rolls back to the savepoint. You can also include the SQL COMMIT statement directly in a PL/SQL program; see "Overview of Transaction Processing in PL/SQL". When an autonomous routine calls a non-autonomous routine, the routines share the same transaction context. Forall can use returning bulk collect into, and sql% rowcount can be used to return the number of updated rows. If you want to get involved, click one of these buttons!

A cursor expression returns a nested cursor. While a subquery is evaluated only once for each table, a correlated subquery is evaluated once for each row. For example, if the main transaction rolls back, nested transactions roll back, but autonomous transactions do not. Each fetch retrieves another row from the same result set.

If the nested table were not an object but a single scalar , the fetch bulk collect into works fine and, as shown, the looping works fine. This technique can avoid joins. See "LOOP Statements".

Scripting on this page enhances content navigation, but does not change the content in any way. This is useful when you want to base an update on the existing values in a row.

In Example 6-13, you bulk-fetch from a cursor into two collections. When you reopen a cursor variable for a different query, the previous query is lost. For example, in the SQL*Plus environment, if your PL/SQL block does not include a COMMIT or ROLLBACK statement, the final state of your transaction depends on what you do after running the block. Since the rows are no longer locked, you cannot fetch from a FOR UPDATE cursor after a commit. When you pass host cursor variables to a PL/SQL block for opening, the query work areas to which they point remain accessible after the block completes, so your OCI or Pro*C program can use these work areas for ordinary cursor operations. In Example 6-23, several ways are shown to open a cursor. The syntax is PRAGMA AUTONOMOUS_TRANSACTION. Example 6-19 Using a Subquery in a Cursor.

You cannot perform BIND and EXECUTE operations on cursor expressions. Autonomous transactions do SQL operations and commit or roll back, without committing or rolling back the main transaction. Example 6-27 Passing a REF CURSOR as a Parameter. However, by definition, autonomous routines never violate the rules read no database state (RNDS) and write no database state (WNDS) no matter what they do. In the above syntax, the given DML operation will be executed for the entire data that is present between lower and higher range.

Instead, you can pass whole queries (not just parameters) to a cursor variable. Similar to cursor attributes BULK COLLECT has %BULK_ROWCOUNT(n) that returns the number of rows affected in the nth DML statement of the FORALL statement, i.e. Naming cursors after database tables is possible but not recommended. To make sure that changes to all three tables are undone, the exception handler executes a ROLLBACK. But, for readability, code the pragma at the top of the section. If you assign an unopened cursor variable to another cursor variable, the second one remains invalid even after you open the first one. TYPE cursorRecordobj AS Object(GEID varchar2(11), --map member function necessary so as to be able to do MULTISET UNION DISTINCT or SET(nestedTable) further ---------------downstream, TYPE DM1_DM2_OBJ_NT AS TABLE of CursorRecordobj, p_out OUT SYS_REFCURSOR,  -- out parameteer sys_refcursor, RETURN DM1_DM2_OBJ_NT;  -- returns a nested table. Example 6-4 Calling the SQL COUNT Function in PL/SQL. When you need precise control over query processing, you can explicitly declare a cursor in the declarative part of any PL/SQL block, subprogram, or package. A cursor variable is more flexible because it is not tied to a specific query. Answer: Here are some working examples of ref cursors. Transactions are not tied to PL/SQL BEGIN-END blocks.

More important, autonomous transactions help you build modular, reusable software components. If a large amount of data is loaded into memory at one time, it will be too stressful for PGA. See "Retrieving Query Results into Collections with the BULK COLLECT Clause". First, you OPEN a cursor variable FOR a multi-row query. For example: You can use a subquery to find the MAX(), MIN(), or AVG() value for a column, and use that single value in a comparison in a WHERE clause. Savepoint names are undeclared identifiers. You usually do not need to write extra code to prevent problems with multiple users accessing data concurrently. Unfortunately, my company is still running on Oracle9i Database, so I have started converting my cursor FOR loops to BULK COLLECTs. It is a %ROWTYPE record whose field names match the column names from the query, and that exists only during the loop. You can perform tests and calculations, display output, or store the results somewhere else. Correct - it fails because a 'fetch' just gives you the individual columns, ORA-06504 - Return types of result set or query do not match. Other OPEN-FOR statements can open the same cursor variable for different queries. To save an attribute value for later use, assign it to a local variable immediately. As arguments to table functions, in the FROM clause of a SELECT statement. When its cursor or cursor variable is opened, %ROWCOUNT is zeroed. To avoid confusion, use different names for cursor parameters and the PL/SQL variables that you pass into those parameters. The OPEN-FOR statement associates a cursor variable with a multi-row query, executes the query, and identifies the result set. I was very happy to learn that Oracle Database 10g will automatically optimize my cursor FOR loops to perform at speeds comparable to BULK COLLECT. Because explicit cursors are so flexible, you can choose from different notations depending on your needs. If one or both cursor variables are weakly typed, they can have different datatypes. INTERSECT returns all distinct rows selected by both queries. To exit normally, you must explicitly commit or roll back all autonomous transactions.

finalTree DM1_DM2_OBJ_NT := DM1_DM2_OBJ_NT(); interimTree DM1_DM2_OBJ_NT := DM1_DM2_OBJ_NT(); sp_get_all_dm1_first_level_dm2(p_geid, v_ref_in , v_varray_in); -- This works but is slow ************************************.

This technique avoids the memory overhead of storing a copy of the result set. When you leave the loop, the cursor is closed automatically. The only exception is where %ROWTYPE is used to define the collection. A single query can return a large set of related values retrieved from multiple tables. Typically, you use comparison operators in the WHERE clause of a data manipulation statement to form predicates, which compare one expression to another and yield TRUE, FALSE, or NULL. The rows are unlocked when you commit or roll back the transaction. You can use variables of type UROWID to store rowids in a readable format. When you query all the columns of a table, you can store the entire result set in a collection of records, which makes it convenient to loop through the results and refer to different columns. %ROWCOUNT yields 0 if an INSERT, UPDATE, or DELETE statement affected no rows, or a SELECT INTO statement returned no rows. You might want to specify a query in one place but retrieve the rows somewhere else, even in another subprogram. For an example, see "Fetching Across Commits". PL/SQL and its clients share a pointer to the query work area in which the result set is stored. That wouldn't work anyway. (A nested transaction's committed changes are not visible to other transactions until the main transaction commits.). Transaction processing is an Oracle feature, available through all programming languages, that lets multiple users work on the database concurrently, and ensures that each user sees a consistent version of data and that all changes are applied in the right order. For DML statements, look at the FORALL statement, which is much faster than coding these statements inside a regular loop. Example 6-24 Cursor Variable Returning a %ROWTYPE Variable. SAVEPOINT marks the current point in the processing of a transaction. If the routine (or any routine called by it) has pending transactions, an exception is raised, and the pending transactions are rolled back. With a cursor variable, you simply pass the reference to that cursor. This technique can be very fast, but also very memory-intensive. When you roll back to a savepoint, any savepoints marked after that savepoint are erased. the whole data will be populated into the collection variable in a single-go. The values of the cursor attributes always refer to the most recently executed SQL statement. Note that, the larger the number of rows you will collect, the more performance improvement you will achieve.

When you query only certain columns, you can store all the results for each column in a separate collection variable. Example 6-46 marks a database trigger as autonomous. Example 6-31 Cursor Variable with Different Return Types. Then, you can execute FETCH repeatedly until all rows have been retrieved, or you can use the BULK COLLECT clause to fetch all rows at once.

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