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Try it Yourself in Java Draw Code-128 in Java Try it Yourself

Try it Yourself using barcode implement for j2se control to generate, create code 128 code set c image in j2se applications. Code-128 TRY IT YOURSELF This chapter has n o Try It Yourself projects. Try It Yourself project 2 in 19, Procedures, extends the material on native dynamic SQL and puts it to use within the context of stored procedures..

This page intentionally left blank Bulk SQL CHAPTER OBJECTIVES In this chapter, you will learn about . The FORALL statement . The BULK COLLECT clause n 1, PL/SQL Conc epts, you learned that the PL/SQL engine sends SQL statements to the SQL engine, which returns results to the PL/SQL engine. The communication between the PL/SQL and SQL engines is called a context switch. A certain amount of performance overhead is associated with these context switches.

However, the PL/SQL language has a number of features that can minimize the performance overhead known as bulk SQL. Generally, if a SQL statement affects four or more rows, bulk SQL may improve performance significantly. Bulk SQL supports batch processing of SQL statements and their results.

It consists of two features the FORALL statement and the BULK COLLECT clause.. LAB 18.1 The FORALL Statement LAB OBJECTIVE After completing this lab, you will be able to . Use the FORALL statement The FORALL stateme nt sends INSERT, UPDATE, or DELETE statements in batches from PL/SQL to SQL instead of one at a time. For example, consider an INSERT statement enclosed in the numeric FOR loop that iterates ten times:. FOR i IN 1..10 LOO jsp code 128c P INSERT INTO table_name VALUES (.

..); END LOOP;.

This INSERT statem ent is sent from PL/SQL to SQL ten times. In other words, ten context switches take place. If you replace the FOR loop with the FORALL statement, the INSERT statement is sent only once from PL/SQL to SQL, yet it is still executed ten times.

In this case, there is only one context switch between PL/SQL and SQL. The FORALL statement has the following structure (the reserved words in brackets are optional):. FORALL loop_counte barcode 128a for Java r IN bounds_clause SQL_STATEMENT [SAVE EXCEPTIONS];. where bounds_claus e is one of the following:. lower_limit..upper_limit INDICES OF collection_name BETWEEN lower_limit..upper_limit VALUES OF collection_name The FORALL stateme Code 128 Code Set A for Java nt has an implicitly defined loop counter variable associated with it. The values of the loop counter variable and the number of loop iterations are controlled by bounds_clause, which has three forms. The first form specifies lower and upper limits for the loop counter.

This syntax is very similar to the numeric FOR loop. The second form, INDICES OF references subscripts of the individual elements of a particular collection. This .

.., collection may be a nested table or an associative array that has numeric subscripts.

. The FORALL Statement DID YOU KNOW A co jboss code 128 code set c llection referenced by the INDICES OF clause may be sparse. In other words, some of its elements have been deleted..

The third form of bounds_clause, VALUES OF references values of the individual elements ...

, of a particular collection, which is either a nested table or an associative array.. WATCH OUT! When yo code 128c for Java u use the VALUES OF option, the following restrictions apply:. . If the collection used in the VALUES OF clause is an associative array, it must be indexed by PLS_INTEGER and BINARY_INTEGER. . The elements of the collection used in the VALUES OF clause must be PLS_INTEGER or BINARY_INTEGER. . When the collection referenced by the VALUES OF clause is empty, the FORALL statement causes an exception. Next, SQL_STATEMEN T is either a static or dynamic INSERT, UPDATE, or DELETE statement that references one or more collections. Finally, the optional SAVE EXCEPTIONS clause allows the FORALL statement to continue even when SQL_STATEMENT causes an exception. Consider the following example that illustrates how the FORALL statement may be used.

This example, as well as other examples in this chapter, uses a test table created specifically for this purpose. The rows from the TEST table can be easily inserted, updated, or deleted without affecting the STUDENT schema or violating any integrity constraints..

FOR EXAMPLE CREATE TABLE test (row_num NUMBER, row_text VARCHAR2(10)); DECLARE -- Define collection types and variables TYPE row_num_type IS TABLE OF NUMBER INDEX BY PLS_INTEGER; TYPE row_text_type IS TABLE OF VARCHAR2(10) INDEX BY PLS_INTEGER; row_num_tab row_num_type; row_text_tab row_text_type; v_total NUMBER; BEGIN -- Populate collections FOR i IN 1..10 LOOP row_num_tab(i) := i; row_text_tab(i) := "row ".

i; END LOOP;. The FORALL Statement FOR EXAMPLE (continued). -- Populate TEST t able FORALL i IN 1..10 INSERT INTO test (row_num, row_text) VALUES (row_num_tab(i), row_text_tab(i)); COMMIT; -- Check how many rows were inserted in the TEST table -- and display it on the screen SELECT COUNT(*) INTO v_total FROM TEST; DBMS_OUTPUT.

PUT_LINE ("There are ". v_total " rows in the TEST table"); END;. As mentioned earli Code 128 Code Set A for Java er, when SQL statements are used with FORALL statements, they reference collection elements. So, in this script, you define two collection types as associative arrays and two collections that are populated using the numeric FOR loop. Next, you populate the TEST table with the data from two collections.

When run, this example produces the following output:.
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