1. PL/SQL Introduction Database 1. Practice

2. Sample Database The schema of the sample database is the following: Drinkers (name, occupation, birthday, salary) Wines (name, type, country) Bars (name, street_number, street, city, tel) Likes (drinker, wine) Frequents (drinker, wine) Sells (bar, wine, price)

3. Blokk A PL/SQL program consists of blocks. A block optionally contains a declaration part, the body of the block must be given, which may be followed by an exception handling part. [DECLARE declarations] BEGIN command [commands]... [EXCEPTION exceptions] END; Note: for the use of labels and GOTO commands consult the Oracle documentation.

4. Declaration of record type Records are heterogenous, complex data types which should be always declared before their use. TYPE name IS RECORD ( field_name type [[NOT NULL] {:= | DEFAULT} expression] [, field_name type [[NOT NULL] {:= | DEFAULT} expression]…);

5. Example for a record type declaration DECLARE TYPE film IS RECORD ( titleVARCHAR2(20) NOT NULL, yearDATE, lengthNUMBER DEFAULT 90, studioVARCHAR2(15));

6. %TYPE, %ROWTYPE %TYPE : is used to refer to a previously declared type which is given to an attribute of a table, or a field of a record, or a variable. %ROWTYPE : returns the record type corresponding to the type of the rows of a table or a cursor. In both cases, whenever there is a change in the type of the referred object, in the corresponding declarations the types are automatically updated.

7. %TYPE, %ROWTYPE example CREATE TABLE Books AS ( titleVARCHAR2(50) NOT NULL, writerVARCHAR2(40) NOT NULL); DECLARE books_rowBooks%ROWTYPE, titleBooks.title%TYPE, …

8. Displaying texts DMBMS_OUTPUT package The most important procedures are – NEW_LINE – PUT – PUT_LINE Before the code of a program using the DMBMS_OUTPUT package the SET SERVEROUTPUT ON command should be issued in order to enable the displaying of texts.

9. Value assignment variable := value Conditional value assignment CASE selector WHEN condition THEN value [WHEN condition THEN value]... [ELSE value] END

10. Example for value assignments SET SERVEROUTPUT ON DECLARE v_date DATE := DATE '1983-05-29'; v_season VARCHAR2(6); BEGIN v_season := CASE WHEN TO_CHAR(v_date, 'MM') IN ('01', '02', '12') THEN 'winter' WHEN TO_CHAR(v_date, 'MM') IN ('03', '04', '05') THEN 'spring' WHEN TO_CHAR(v_date, 'MM') IN ('06', '07', '08') THEN 'summer' WHEN TO_CHAR(v_date, 'MM') IN ('09', '10', '11') THEN 'autumn' ELSE 'error' END; DBMS_OUTPUT.PUT_LINE (v_season); END;

11. SELECT INTO statement I. SET SERVEROUTPUT ON DECLARE v_occ Drinkers.occupation%TYPE; BEGIN SELECT occupation INTO v_occ FROM Drinkers WHERE name = 'Maria'; DBMS_OUTPUT.PUT_LINE('The occupation of Maria is: ' || v_occ); END; Note: if the SQL query returns more than one row or it does not return any row, then an exception is thrown.

12. SELECT INTO statement II. SET SERVEROUTPUT ON DECLARE v_occDrinkers.occupation%TYPE; v_birthDrinkers.birthday%TYPE; BEGIN SELECT occupation, birthday INTO v_occ, v_birth FROM Drinkers WHERE name = 'Maria'; DBMS_OUTPUT.PUT_LINE('Occupation: ' || v_occ || ' Birthday: ' || v_birth); END;

13. A SELECT INTO utasítás III. SET SERVEROUTPUT ON DECLARE v_rowDrinkers%ROWTYPE; BEGIN SELECT * INTO v_row FROM Drinkers WHERE name = 'Maria'; DBMS_OUTPUT.PUT_LINE('Occupation: ' || v_row.occupation || ' Birthday: ' || v_row.birthday); END;

14. IF-THEN-ELSE IF condition THEN command [command].... [ELSIF condition THEN command [command]....]... [ELSE command [command]....] END IF;

15. Example for an if-then-else statement SET SERVEROUTPUT ON DECLARE v_number NUMBER := -5; v_abs_val NUMBER; BEGIN IF v_number >= 0 THEN v_abs_val := v_number; ELSE v_abs_val := -1 * v_number; END IF; DBMS_OUTPUT.PUT_LINE ('The absolute value of: ' || v_number || ' is ' || v_abs_val ); END;

16. CASE CASE [selector] WHEN {condition | expression} THEN command [command ]... [WHEN {condition | expression} THEN command [command ]...]... [ELSE command [command ]...] END CASE;

17. Example for a CASE statement SET SERVEROUTPUT ON DECLARE mark NUMBER(1) := 4; BEGIN CASE mark WHEN 1 THEN DBMS_OUTPUT.PUT_LINE('failed'); WHEN 2 THEN DBMS_OUTPUT.PUT_LINE('bad'); WHEN 3 THEN DBMS_OUTPUT.PUT_LINE('not bad'); WHEN 4 THEN DBMS_OUTPUT.PUT_LINE('good'); WHEN 5 THEN DBMS_OUTPUT.PUT_LINE('excellent'); ELSE DBMS_OUTPUT.PUT_LINE('There is no such mark.'); END CASE; END;

18. Simple loop Syntax: LOOP command [command]... END LOOP; Example: DECLARE fakt NUMBER:=1; i PLS_INTEGER:=2; BEGIN LOOP fakt:=fakt*i; EXIT WHEN fakt > 1000; i:=i+1; END LOOP; DBMS_OUTPUT.PUT_LINE(' The factorial is: ' || fakt); END;

19. WHILE loop Syntax: WHILE condition LOOP command [command]... END LOOP; Example: DECLARE v_exp NUMBER :=1; BEGIN WHILE v_exp < 10000 LOOP v_exp := 2* v_exp; END LOOP; DBMS_OUTPUT.PUT_LINE (v_exp); END;

20. FOR loop Syntax: FOR variable IN [REVERSE] lower_bound..upper_bound LOOP command [command]... END LOOP; The type of variable is automatically set to PLS_INTEGER. By using the EXIT command one can terminate a loop statement. The program continues with the next command after the loop. In other words, the effect of EXIT is the same as that of the break statement in C++.

21. Example for a FOR statement SET SERVEROUTPUT ON DECLARE v_sum NUMBER := 0; BEGIN FOR i in 1..100 LOOP v_sum := v_sum + i; END LOOP; DBMS_OUTPUT.PUT_LINE('The sum of the first 100 numbers is: ' || v_sum); END;

22. Exercises Write a program which displays the following data: – the  I love the whole world  string – the country, where Cave Geisse Nature is produced – the occupation and birthday of Hannah – the number of those who visit Bar do Mineiro – the smallest number which is greater than 10000 and is divisible by 7 – those prime numbers that are less than 100.