Chapter 10 Oracle9i Developer: PL/SQL Programming Introduction to Dynamic SQL and Object Technology

Objectives Create dynamic SQL Use object technology

Brewbean’s Challenge Add flexibility to queries such as allowing shoppers to determine if they want to search product names or descriptions Explore potential capabilities of object technology features for providing greater data consistency and control

Dynamic SQL Allows identifiers such as column and table names to be provided at runtime Two mechanisms available: DBMS_SQL package (Oracle7) Native dynamic SQL (Oracle8)

DBMS_SQL – DML Example CREATE OR REPLACE PROCEDURE dyn_dml_sp (p_col VARCHAR2, p_price NUMBER, p_id NUMBER) IS lv_cursor INTEGER; lv_update VARCHAR2(150); lv_rows NUMBER(1); BEGIN --Open Cursor lv_cursor := DBMS_SQL.OPEN_CURSOR;

DBMS_SQL (continued) --Create DML statement lv_update := 'UPDATE bb_product SET ' || p_col || ' = :ph_price WHERE idProduct = :ph_id'; --Parse the statement DBMS_SQL.PARSE(lv_cursor, lv_update, DBMS_SQL.NATIVE); --Associate parameters with placeholders in the statement DBMS_SQL.BIND_VARIABLE(lv_cursor, ':ph_price', p_price); DBMS_SQL.BIND_VARIABLE(lv_cursor, ':ph_id', p_id);

DBMS_SQL (continued) --Run the DML statement lv_rows := DBMS_SQL.EXECUTE(lv_cursor); --Close the cursor DBMS_SQL.CLOSE_CURSOR(lv_cursor); --Save changes COMMIT; --Check how many rows affected DBMS_OUTPUT.PUT_LINE(lv_rows); END;

DBMS_SQL

DBMS_SQL – Query Example CREATE OR REPLACE PROCEDURE dyn_query1_sp (p_col IN VARCHAR2, p_value IN VARCHAR2) IS lv_query LONG; lv_status INTEGER; lv_cursor INTEGER; lv_col1 NUMBER(2); lv_col2 VARCHAR2(25); lv_col3 NUMBER(6,2); lv_col4 NUMBER(5,1);

DBMS_SQL (continued) BEGIN --Open the cursor lv_cursor := DBMS_SQL.OPEN_CURSOR; --Build the query lv_query := 'SELECT idProduct, productname, price, stock FROM bb_product WHERE '|| UPPER(p_col) ||' = ' || 'UPPER(:ph_value)'; --Parse the statement DBMS_SQL.PARSE(lv_cursor, lv_query, DBMS_SQL.NATIVE); --Identify data types for each item selected DBMS_SQL.DEFINE_COLUMN(lv_cursor, 1, lv_col1); DBMS_SQL.DEFINE_COLUMN(lv_cursor, 2, lv_col2, 25); DBMS_SQL.DEFINE_COLUMN(lv_cursor, 3, lv_col3); DBMS_SQL.DEFINE_COLUMN(lv_cursor, 4, lv_col4);

DBMS_SQL (continued) --Associate placeholder with a parameter DBMS_SQL.BIND_VARIABLE(lv_cursor, ':ph_value', p_value); --Execute the query lv_status := DBMS_SQL.EXECUTE(lv_cursor); --Fetch row returned and place into PL/SQL variables IF (DBMS_SQL.FETCH_ROWS(lv_cursor) > 0) THEN DBMS_SQL.COLUMN_VALUE(lv_cursor, 1, lv_col1); DBMS_SQL.COLUMN_VALUE(lv_cursor, 2, lv_col2); DBMS_SQL.COLUMN_VALUE(lv_cursor, 3, lv_col3); DBMS_SQL.COLUMN_VALUE(lv_cursor, 4, lv_col4); DBMS_OUTPUT.PUT_LINE(lv_col1||' '||lv_col2||' '||lv_col3||' '||lv_col4); END IF; --Close cursor DBMS_SQL.CLOSE_CURSOR(lv_cursor); END;

DBMS_SQL

Native Dynamic SQL Simpler coding More efficient processing Limited capabilities compared to DBMS_SQL package Two methods: EXECUTE IMMEDIATE OPEN FOR

Native Dynamic SQL Example CREATE OR REPLACE PROCEDURE dyn_query3_sp (p_col IN VARCHAR2, p_value IN VARCHAR2) IS lv_query VARCHAR2(200); lv_id bb_product.idProduct%TYPE; lv_name bb_product.productname%TYPE; lv_price bb_product.price%TYPE; lv_stock bb_product.stock%TYPE; BEGIN --use a variable to hold the query construction to -- make it more readable

Native Dynamic SQL (continued) lv_query := 'SELECT idProduct, productname, price, stock FROM bb_product WHERE UPPER(' || p_col || ') = UPPER(:ph_value)'; --Run the dynamic query supplying variables to hold the -- return values in the INTO clause and associate the -- parameter to the placeholder with the USING clause EXECUTE IMMEDIATE lv_query INTO lv_id, lv_name, lv_price, lv_stock USING p_value; DBMS_OUTPUT.PUT_LINE(lv_id||' '||lv_name||' ' ||lv_price||' '||lv_stock); END;

Native Dynamic SQL

DBMS_SQL vs. Native Dynamic SQL Use native dynamic SQL when: The number and types of columns to be used is known The number and type of bind variables is known To perform DDL Executing the statement only once or twice User-defined types such as object and collections are used (not supported by DBMS_SQL) Fetching rows of data into PL/SQL records (not supported by DBMS_SQL) SQL statement is less than 32KB in size

Object Technology Object Types Object Methods Object Relations Object Views

Object types Represent an entity such as an address or a person Defined with attributes and methods Can be used as a data type for a table column Can contain multiple data elements or attributes

Create an Object Type CREATE OR REPLACE TYPE addr_ot AS OBJECT (street1 VARCHAR2(25), street2 VARCHAR2(25), city VARCHAR2(25), state CHAR(2), zip NUMBER(9) );

Use Object Type CREATE TABLE bb_order (ord_id NUMBER(4), cust_id NUMBER(4), ord_date DATE, total NUMBER(6,2), bill_addr addr_ot, ship_addr addr_ot );

Object Type Constructor DECLARE lv_bill addr_ot; lv_ship addr_ot; BEGIN lv_bill := addr_ot('11 Bush Dr' ,NULL, 'Savannah', 'GA',346668229); lv_ship := addr_ot('812 Scott Lane','Apt #52','Savannah','GA',346668227); INSERT INTO bb_order VALUES (102,31,'11-NOV-03’ ,34.50,lv_bill,lv_ship); END;

DESCRIBE command

Methods Add program units to object types Referred to as members Similar to package creation Add function: ALTER TYPE addr_ot ADD MEMBER FUNCTION lbl_print RETURN VARCHAR2;

Object Type Body

Object Relations Create customer object type: CREATE TYPE cust_ot AS OBJECT (cust_id NUMBER(4), first VARCHAR2(15), last VARCHAR2(20), email VARCHAR2(25), phone NUMBER(10) ); Create customer table: CREATE TABLE bb_cust OF cust_ot (PRIMARY KEY (cust_id));

Object Relations (continued) Create orders object type: CREATE TYPE ord_ot AS OBJECT (ord_id NUMBER(4), cust_ref REF cust_ot, ord_date DATE, total NUMBER(6,2)); CREATE TABLE bb_ord OF ord_ot (PRIMARY KEY (ord_id));

Object Relations (continued) Use REF variable to establish relation: INSERT INTO bb_cust VALUES (cust_ot(12,'Joe','Cool','jcool@yahoo.com', 7773335555)); INSERT INTO bb_ord SELECT ord_ot(1,REF(c),SYSDATE,24.50) FROM bb_cust c WHERE cust_id = 12; COMMIT;

REF pointers Does not prevent broken relations like a foreign key constraint

Object Views Provide a layer on top of traditional database designs to enable object features OBJECT OID identifies unique view row identifier CAST and MULTISET handle subquery mapping to view elements

Object View Example CREATE TYPE bask_ot AS OBJECT (idBasket NUMBER(5), total NUMBER(7,2)) / CREATE TYPE bask_tab AS TABLE OF bask_ot CREATE TYPE shop_ot AS OBJECT (idShopper NUMBER(4), last_name VARCHAR2(20), city VARCHAR2(20), idBasket bask_tab)

Object View Example CREATE VIEW shop_vu OF shop_ot WITH OBJECT OID(idShopper) AS SELECT s.idShopper, s.lastname, s.city, CAST(MULTISET(SELECT idBasket, total FROM bb_basket b WHERE b.idShopper = s.idShopper) AS bask_tab) FROM bb_shopper s;

Summary Dynamic SQL allows identifiers and DDL statements to process within PL/SQL DBMS_SQL package and native dynamic SQL are two mechanisms providing dynamic SQL capabilities Native dynamic SQL is simpler to code and executes more efficiently Object types represent an entity which can contain multiple data attributes and program units

Summary Program units in object types are called methods Relationships between object rows are established using REF variables Object views provide a mechanism to use object technology features with a traditional database design