The SQL Developer tool provides a way to develop, unit test, and handle version control. In SQL Developer, you can set up basic frameworks for the database objects. ## Statements generated by SQL Developer when creating new object ## Create procedure with two parameters passed in CREATE PROCEDURE EXAMPLE_PROC1 ( PARAM1 IN VARCHAR2 , PARAM2 IN NUMBER )AS BEGIN NULL; END EXAMPLE_PROC1 ; / ## Create trigger on insert CREATE TRIGGER EXAMPLE_TRIGGER1 BEFORE INSERT ON EMP REFERENCING OLD AS OLD NEW AS NEW FOR EACH ROW WHEN (DEPTNO=10) BEGIN NULL; END; / As noted in Table 9-1, a semicolon (;) is the delimiter that marks the end of the block. The forward slash (/) says to execute the code in SQL*Plus. NOTE SQL Developer and some of the other tools have ways to execute statements with a run or run script statement, which will run the code without the forward slash. However, in SQL*Plus, the / is required to have the code run, like saying “Go.” In SQL Server, you get an identity column, but Oracle doesn’t have an identity type. Insert triggers are useful for generating IDs for primary keys. Using a sequence, you can retrieve the next value for a unique number to be used as an ID. You could also use a procedure for inserts to pull in the 242 Oracle Database Administration for Microsoft SQL Server DBAs next value from the sequence without a trigger. This could be used on every insert, as long as the application does not rely on ad hoc queries for inserts. ## Trigger for sequences and populating identity column create sequence order_id_seq start with 1 increment 1; create or replace trigger trg_i_orders before insert for each row begin select order_id_seq.nextval into :new.order_id from dual; end; / You cannot use a role to grant permissions to the objects in a procedure that the procedure owner is using in that code. Permissions for the objects that are being accessed and used in the code must be explicitly granted to the procedure owner. Also worth mentioning is a difference in create and replace operations with the database programming languages. In SQL Server, the object is dropped first and then re-created, normally after first checking if the object exists. In Oracle, there is no need to check first, because the create or replace command will create the object if it is not there or replace the existing object with the new code. This works for stored procedures, packages, triggers, and views. Packages and Package Bodies Along with the usual objects of triggers, functions, and procedures, Oracle also has packages and package bodies. The package is the collection of the definitions of the procedures and functions that are found in the package body. Variables, constants, and cursors are also declared in the package definition, and can be used in the subprograms found in the package body. Figure 9-1 shows an example of using SQL Developer to create the framework for a package. Using subprograms makes the code more modular, so it is easier to manage changes to programs and global variables. Since the whole package is loaded into memory, execution becomes faster; it’s not necessary to recompile because of dependencies on other programs. Error handling can also be defined at the package level for all of the subprograms to use, which makes programming more consistent and avoids repeating the same steps in several different procedures. Chapter 9: PL/SQL 243 Here is an example of defining a package with package body, with error handling (discussed later in this chapter) and variable declarations: create or replace package modify_product_info as TYPE ProductRec is record (prod_id number,longname varchar2(50)); cursor desc_prod return ProductRec; procedure upd_prod_name(v_prod_id in varchar2); procedure ins_new_prod (v_prod_id in varchar2,v_longname in varchar2); function get_prod_id(v_prod_name in varchar2) RETURN ProductRec; procedure raise_app_error(v_error_code in varchar2, v_text in varchar2, v_name1 in varchar2, v_value1 in varchar2); END modify_product_info; / create or replace package body modify_product_info as cursor desc_prod return ProductRec is select prod_id, prod_name from orders; 244 Oracle Database Administration for Microsoft SQL Server DBAs FIGURE 9-1. Creating a new package in SQL Developer procedure upd_prod_name(v_prod_id in number) is var_count number; BEGIN update products set prod_name = … EXCEPTION WHEN OTHERS THEN Rollback; raise_app_error(v_error_code => 'UNANTICIPATED-ERROR', v_text => 'Details…',v_name1 => 'TABLE_NAME'); END upd_prod_name; function get_prod_id(v_prod_name in varchar2) RETURN ProductRec is var_prod_id prod_id_type%TYPE; BEGIN select prod_id into var_prod_id from orders where return var_prod_id; EXCEPTION WHEN NO_DATA_FOUND raise_app_error(v_error_code => 'NO DATA…' END get_prod_id; ## Define other procedures and functions END modify_product_info; This example shows the flow of the package and package body definition. As you can see, the functions and procedures are defined just with the input and output procedures in the package. The functions and stored procedures are then listed again in the body of the package with the details of the procedure and statements to be processed. If the package header has a procedure listed, the body must contain the definition. Of course, the code is filled in with processing, conditional statements, data processing, and so on. Chapter 9: PL/SQL 245 Triggers In both SQL Server and Oracle environments, triggers are available on logon, object changes, and data changes. Triggers can be fired for events such as startup or shutdown and when inserts, updates, and deletes are issued. The concept of the trigger is the same in both Oracle and SQL Server, but there are some differences in the types available and when they execute. Table 9-2 summarizes the types of triggers available on both platforms. The triggers on the database system events, such as startup, shutdown, and server message events, can be used for auditing or changing session parameters. ##Audit logins via sqlplus into a table create or replace trigger after logon on database begin insert into logon_from_sqlplus (user_name,logon_time) select username,sysdate from v$session where program='sqlplus.exe'; end; / ##Trigger to prevent dropping of objects create or replace trigger drop_not_allowed before drop on database begin RAISE_APPLICATION_ERROR(-20001,'Drop table not allowed'); end; / 246 Oracle Database Administration for Microsoft SQL Server DBAs SQL Server Triggers Oracle Triggers DML triggers After Instead of DML triggers Before and after Instead of Statement and row DDL triggers DDL triggers Event triggers, system and user Event triggers, system and user TABLE 9-2. SQL Server and Oracle Trigger Types ##Alter the session to have a different parameter setting create or replace trigger after logon on database begin execute immediate 'alter session set optimizer_mode=FIRST_ROWS'; end; / The EXECUTE IMMEDIATE statement executes a SQL statement that can’t be executed normally in a block of code, such as ALTER SESSION, ALTER TABLE, and other object changes. Dynamic SQL statements can also be built and then executed using the EXECUTE IMMEDIATE statement in the code of triggers, procedures, or functions. sql_stmt varchar2(300); var_col varchar2(30); begin select column_name into var_col from user_tab_cols where table_name=v_table and column_name=v_column; Sql_stmt := 'update '||v_table|| ' set price = :1 where ' || var_col || ' =:2'; execute immediate sql_stmt USING amout, column_value; Triggers on tables that fire on update, insert, and delete offer some different options in Oracle than in SQL Server. In SQL Server, the triggers fire after the change, or they can do something instead of the action. Oracle triggers have the option of executing before or after, and they can be fired for each row that is changed or once for the whole statement. So, if a delete is run against the table, the statement-level trigger will fire once for the whole delete, which would be good for an audit record. The row-level trigger is useful for inserting the data that is being changed into another table, for example. The BEFORE trigger is useful for validating the data and checking that the change should be performed. Being able to execute these actions before the change occurs could prevent rollbacks, and even disallow changes if an incorrect role or application is attempting to make them. The BEFORE trigger also allows for the adjustment of values or determination of values for another column, and could help maintain referential relationships. For use with row-level triggers, the variables :NEW and :OLD refer to the new Chapter 9: PL/SQL 247 and existing values for the columns, respectively. With BEFORE triggers, the old values cannot be updated, but the new values can change in the trigger body and be the “new” new values. BEFORE triggers are used on tables; they cannot be used on views. AFTER and BEFORE triggers are used in combination with the statement and row triggers, which create the four types of triggers for actions on tables. ## Trigger examples create or replace trigger trg_u_customers after update on customers for each row begin update orders set customer_name=:new.customer_name where custumer_namer=:old.customer_name; end; / ## Trigger example to combine update, insert and deletes create or replace trigger trg_iud_customers after insert or update or delete on customers for each row declare v_order_date date; BEGIN v_order_date := sysdate; if INSERTING THEN INSERT into orders values(order_seq.nextval, :new.customer_id, order_details,v_order_date); other possible inserts or code end if; if DELETING THEN INSERT into customer_hist_tbl values(:old.customer_id,:old.customer_name, :old_cust_details); end if; if UPDATING ('CUSTOMER_NAME') THEN update customer_hist_tbl set customer_name=:old.customer_name where customer_id=:new.customer_id; end if; END; / 248 Oracle Database Administration for Microsoft SQL Server DBAs Updates and Conditions Before getting into the transaction part of the procedures and other useful information about PL/SQL, let’s take a brief look at UPDATE statements, which tend to be very different in SQL Server and Oracle. The transition from doing SQL Server updates to handling them in Oracle is not easy. It may take several tries to not think in SQL Server syntax and get the correct statement for an Oracle update. Table 9-3 shows a couple of examples. One difference is that in Oracle, you can group the columns being updated to set more than one column equal to the SELECT statement. Another is that instead of needing to list the table again for joins, Oracle can use the table being updated to join against in the query. To test the SQL Server UPDATE statement, you can just run the query after the FROM to Chapter 9: PL/SQL 249 Update SQL Server Example Oracle Example Update one column UPDATE titles SET ytd_sales = t.ytd_sales + s.qty FROM titles t, sales s WHERE t.title_id = s.title_id UPDATE titles t SET ytd_sales= (SELECT t.ytd_sales + s.qty FROM sales s WHERE t.title_id=s.title_id) Update multiple columns UPDATE orders SET Customer_id=c.customer_id, item_id=p.item_id FROM (SELECT c.customer_id, p.item_id FROM products p, customers c, orders o WHERE c.order_id=o.order_id and o.product_name=p.product_ name) WHERE order_id=1234 UPDATE orders o SET (customer_id, item_id)= (SELECT c.customer_ id,p.item_id FROM products p, customers c WHERE c.order_id=o.order_id and o.product_nsme= p.product_name) WHERE o.order_id=1234 TABLE 9-3. UPDATE Statements in SQL Server and Oracle know which values you are getting. To test the update in Oracle, you can pull the update table into the query. SQLPLUS> SELECT c.customer_id,p.item_id FROM products p, customers c, orders o WHERE c.order_id=o.order_id and o.product_nsme=p.product_name) SQLPLUS> UPDATE orders o SET (customer_id, item_id) = (select c.customer_id,p.item_id FROM products p, customers c WHERE c.order_id=o.order_id and o.product_nsme=p.product_name) WHERE o.order_id=1234; It does take some practice to get used to writing the updates differently. Other statements that select with joins translate fairly easily. Also, INSERT and DELETE statements are similar. Since we are looking at some of the SQL statements here before putting them into the PL/SQL code, another function worth mentioning is DECODE. Like CASE (which Oracle also has), DECODE is useful for conditions. SQLPLUS> select DECODE(deptno, 10, 'Technology',20,'HR', 30, 'Accounting','General') from departments; ## start with the value and if it matches then substitute the NEXT value ## the last value is the default which is optional Ranges and not equal values are probably easier to define in a CASE statement, but DECODE is useful for other situations. For example, you might use it for date or number comparisons: SQLPLUS> select DECODE(date1-date2)-abs(date1-date2), 0, 'Date 1 is greater than Date 2, 'Otherwise Date 2 is greater than Date 1') from list_date_table; These examples might be useful in developing your code and writing more effective PL/SQL. Transactions Transactions are a main reason for writing procedures, and planning transaction size, commits, and rollback points are part of good procedures. Transactions that are too big will cause issues like filling up log space or blocking in SQL Server, and possibly fill up the undo tablespace in Oracle. Transactions that 250 Oracle Database Administration for Microsoft SQL Server DBAs are too small can have too many commits and checkpoints, which can slow down processing. The starting point for a transaction is defining the blocks of code to be executed, where to roll back or commit, and then working in this framework to define transaction size. SQL Server has BEGIN TRAN, and then you can COMMIT or ROLLBACK TRAN after completion of the statement. Beginning a Transaction Oracle has a BEGIN statement to start the transaction, which works just like BEGIN TRAN in SQL Server. For marking a point to be able to commit or roll back to, you use SAVEPOINT transaction_name. This will start the transaction either in a block of code or a stored procedure, or even in a SQL*Plus session before executing a SQL statement. SQLPLUS> begin insert into emp values('Mandy',10); end; / PL/SQL procedure successfully completed. SQLPLUS> select * from emp; EMP_NAME EMP_DEPT Mandy 10 SQLPLUS> begin insert into emp values('Emily',20); insert into emp values('Gabrielle',50); savepoint savepoint_before_delete; delete emp where emp_dept=10; end; / PL/SQL procedure successfully completed. SQLPLUS> select * from emp; EMP_NAME EMP_DEPT Emily 20 Gabrielle 50 SQLPLUS> rollback to savepoint_before_delete; Rollback complete. SQLPLUS> select * from emp; Chapter 9: PL/SQL 251 . drop_not_allowed before drop on database begin RAISE_APPLICATION_ERROR(-20001,'Drop table not allowed'); end; / 246 Oracle Database Administration for Microsoft SQL Server DBAs SQL Server Triggers Oracle. if; END; / 248 Oracle Database Administration for Microsoft SQL Server DBAs Updates and Conditions Before getting into the transaction part of the procedures and other useful information about PL /SQL, . log space or blocking in SQL Server, and possibly fill up the undo tablespace in Oracle. Transactions that 250 Oracle Database Administration for Microsoft SQL Server DBAs are too small can have