ISYS 365 – SQL*Plus Environment

2 Agenda What is SQL*Plus? Command Line Editor Useful SQL*Plus Commands Useful System Tables What is PL/SQL? PL/SQL Constructs

3 What is SQL*Plus? Oracle’s development environment Used to write, test and debug SQL and PL/SQL code Hasn’t changed much in 20 years

4 Command Line Editor list or list # change Example: /Featuer/Feature (can use any delimiter) del del (current line only) del 3 7 (range of lines) del 2 LAST (deletes from line 2 to the end of the buffer) Do NOT use the word “delete” clear buffer: clears out the SQL statement

5 Command Line Editor append Places text at the end of the current line without any spaces between the existing text & the appended text input

6 Useful SQL*Plus Commands set headsep: identifies the character that tells SQL*Plus when to split a title or column onto 2 or more lines Default character: | SQL> SELECT LNAME "Last_Name|Of|Employee" will display Last_Name Of Employee Set headsep ! ttitle: sets the title at the top of each page ttitle ‘Sales by Product During 1901!Second Six Months’ If title should display an apostrophe, then use two single quotes btitle: sets the title at the bottom of each page

7 Useful SQL*Plus Commands column: tells SQL*Plus how to handle columns Can be used to re-label column headings column Item heading ‘What Was!Sold’ Can be used to specify column format column Item format a18 column Rate format zero tells SQL*Plus to pad the number with a zero (if necessary) 999,999, Can be used to truncate data in column column Item truncated (OR column Item trunc) Can be used to wrap info column Item word_wrapped

8 Useful SQL*Plus Commands column: tells SQL*Plus how to handle columns Can be used to specify column format Alphanumeric: column Item format a18 Numeric: column Rate format Use nines and zeros to specify the numeric pattern Examples: (a) 999,999,999 (b) COLUMN Salary FORMAT $999, See “numeric formatting” in Oracle Complete Reference

9 Useful SQL*Plus Commands break on: tells SQL*Plus where to break for subtotals and totals break on Item skip 2 will not repeat the value in the Item column Create one line for each unique Item value and skip 2 lines break on Item duplicate skip 2 will repeat the value in the Item column must be coordinated with the order by clause break on report tells SQL*Plus to provide a grand total for the report Example: break on Item skip 2 on report break on report on Item skip 2 compute sum: tells SQL*Plus to calculate subtotals works in conjunction with the break on command

10 Useful SQL*Plus Commands Basic rules for computing subtotals & totals: Every break on must have a related order by Consecutive break on commands will override the previous break on command To create both subtotals & totals, combine the break on instructions as follows break on X skip # on report OR break on report on X skip # where X = column name & # = lines to skip between sections Every compute sum must have a related break on Clear breaks and computes before setting up new ones

11 Useful SQL*Plus Commands set linesize sets the maximum number of characters allowed on any line; usually 70 or 80 set pagesize sets the maximum number of lines per page; usually 66 lines set newpage sets the number of blank lines between pages

12 Useful SQL*Plus Commands spool & spool off Example: spool test.sql run (/) start save saves the SQL statements, but not the SQL*Plus commands Example: save example.sql (or save example.sql replace) store saves the current SQL*Plus environment Example: store set my_settings.sql create (or …replace or …append)

13 Useful SQL*Plus Commands To check the current settings column (or column column_name) ttitle btitle break compute show headsep show linesize show pagesize show newpage

14 Useful SQL*Plus Commands To clear the current settings ttitle off btitle off clear columns clear breaks clear computes

15 Useful System Tables User_Constraints Useful fields: constraint_name, table_name, constraint_type constraint_type: C, P, R & U User_Cons_Columns Useful fields: constraint_name, column_name, position SELECT column_name FROM user_cons_columns WHERE constraint_name=‘SYS_C ’; Retrieving constraints defined by the user WHERE CONSTRAINT_NAME NOT LIKE '%SYS%';

16 Useful System Tables user_sequences Contains sequences owned by the current user user_errors Contains compilation errors for the current user Use the ‘show errors’ SQL*Plus command to view the errors in the user_errors table

17 What Is PL/SQL? PL/SQL stands for Procedural Language operating on or using SQL Combines the flexibility of SQL (4GL) with the power and configurability of the procedural constructs of a 3GL Extends SQL by adding 3GL constructs such as: Variables and types (predefined and user defined) Control Structures (IF-THEN-ELSE, Loops) Procedures and functions Object types and methods

18 PL/SQL Constructs PL/SQL based on Ada language constructs Block Structure Error Handling Variables and Types Conditionals Looping Constructs Cursors

Introduction to PL / SQL Chapter 1

20 What Is PL / SQL PL/SQL stands for Procedural Language operating on or using SQL Combines power and flexibility of SQL (4GL) with procedural constructs of a 3GL Extends SQL by adding Variables and types Control Structures Procedures and functions Object types and methods

21 File 3gl_4gl.sql Demonstrates both SQL and PL/SQL commands DECLARE v_NewMajor VARCHAR2(10) := 'History'; v_FirstName VARCHAR2(10) := 'Scott'; v_LastName VARCHAR2(10) := 'Urman'; BEGIN UPDATE students SET major = v_NewMajor WHERE first_name = v_FirstName AND last_name = v_LastName; IF SQL%NOTFOUND THEN INSERT INTO students (ID, first_name, last_name, major) VALUES (student_sequence.NEXTVAL, v_FirstName, v_LastName, v_NewMajor); END IF; END; /

22 Client-Server Model SQL results in many network trips, one for each SQL statement PL/SQL permits several SQL statements to be bundled into a single block Results in fewer calls to database Less network traffic faster response time

23 Features of PL / SQL Block Structure Error Handling Variables and Types Looping Constructs Cursors

24 Features of PL / SQL Block Structure Basic unit of PL/SQL is a block Three possible sections of a block Declarative section Executable section Exception handling A block performs a logical unit of work in the program Blocks can be nested

25 Features of PL / SQL Error Handling Exception handling section permits the user to trap and respond to run-time errors Exceptions can be associated with Predefined Oracle errors User-defined errors

26 File Error.sql Illustrates an exception handler DECLARE v_ErrorCode NUMBER;-- Code for the error v_ErrorMsg VARCHAR2(200);-- Message text for the error v_CurrentUser VARCHAR2(8);-- Current database user v_Information VARCHAR2(100);-- Information about the error BEGIN /* Code which processes some data here */ NULL; -- (continued)

27 File Error.sql Illustrates an exception handler EXCEPTION WHEN OTHERS THEN v_ErrorCode := SQLCODE; v_ErrorMsg := SQLERRM; v_CurrentUser := USER; v_Information := 'Error encountered on ' || TO_CHAR(SYSDATE) || ' by database user ' || v_CurrentUser; INSERT INTO log_table (code, message, info) VALUES (v_ErrorCode, v_ErrorMsg, v_Information); END; /

28 Features of PL / SQL Variables and Types A variable is a named location in memory that: can be read from assigned a value Declared in the declaration section Variables have a specific type associated with them Can be same type as database columns

29 Features of PL / SQL Looping Constructs A loop allows execution of a set of statements repeatedly Types of loops Simple loop Numeric For loop While loop

30 File SimpleLoop.sql Demonstrates a simple loop DECLARE v_LoopCounter BINARY_INTEGER := 1; BEGIN LOOP INSERT INTO temp_table (num_col) VALUES (v_LoopCounter); v_LoopCounter := v_LoopCounter + 1; EXIT WHEN v_LoopCounter > 50; END LOOP; END; /

31 File NumericLoop.sql Demonstrates a numeric FOR loop BEGIN FOR v_LoopCounter IN LOOP INSERT INTO temp_table (num_col) VALUES (v_LoopCounter); END LOOP; END; /

32 Features of PL / SQL Cursors A cursor creates a named context area as a result of executing an associated SQL statement Permits the program to step through the multiple rows displayed by an SQL statement

33 File CursorLoop.sql Demonstrates a cursor fetch loop DECLARE v_FirstName VARCHAR2(20); v_LastName VARCHAR2(20); CURSOR c_Students IS SELECT first_name, last_name FROM students; BEGIN OPEN c_Students; LOOP FETCH c_Students INTO v_FirstName, v_LastName; EXIT WHEN c_Students%NOTFOUND; /* Process data here */ END LOOP; CLOSE c_Students; END;

34 File Conditional.sql Illustrates a conditional statement DECLARE v_TotalStudents NUMBER; BEGIN SELECT COUNT(*) INTO v_TotalStudents FROM students; -- (continued)

35 File Conditional.sql Illustrates a conditional statement IF v_TotalStudents = 0 THEN INSERT INTO temp_table (char_col) VALUES ('There are no students registered'); ELSIF v_TotalStudents < 5 THEN INSERT INTO temp_table (char_col) VALUES ('There are only a few students registered'); ELSIF v_TotalStudents < 10 THEN INSERT INTO temp_table (char_col) VALUES ('There are a little more students registered'); ELSE INSERT INTO temp_table (char_col) VALUES ('There are many students registered'); END IF; END; /

36 File PrintStudents.sql Illustrates a stored procedure CREATE OR REPLACE PROCEDURE PrintStudents( p_Major IN students.major%TYPE) AS CURSOR c_Students IS SELECT first_name, last_name FROM students WHERE major = p_Major; BEGIN FOR v_StudentRec IN c_Students LOOP DBMS_OUTPUT.PUT_LINE(v_StudentRec.first_name || ' ' || v_StudentRec.last_name); END LOOP; END; /

37 File PrintStudents.sql Illustrates a stored procedure BEGIN PrintStudents ('Computer Science'); END; /

38 Online Code All of the named examples used in the book are on the accompanying CD

39 Example Tables / Views Tables used throughout text classes – describes the classes available for the students to take debug_table – used during debugging sessions log_table – records Oracle errors major_stats – holds statistics generated about different majors registered_students – contains information about the classes students are currently taking

40 Example Tables / Views Tables used throughout text rooms – holds information about the classrooms available RS_audit – used to record changes made to registered students student_sequence – generates unique values for the primary key of the students students – contains information about students attending the school temp_table – stores temporary data

41 File tables.sql PROMPT student_sequence... DROP SEQUENCE student_sequence; CREATE SEQUENCE student_sequence START WITH INCREMENT BY 1; PROMPT students table... DROP TABLE students CASCADE CONSTRAINTS; CREATE TABLE students ( id NUMBER(5) PRIMARY KEY, first_name VARCHAR2(20), last_name VARCHAR2(20), major VARCHAR2(30), current_credits NUMBER(3) ); …

42 Example Tables classes CREATE TABLE classes ( departmentCHAR (3), courseNUMBER (3), description VARCHAR2 (2000), max_studentsNUMBER (3), current_studentsNUMBER (3), num_creditsNUMBER (1), room_idNUMBER (5), CONSTRAINT classes_department_course PRIMARY KEY (department, course), CONSTRAINT classes_room_id FOREIGN KEY (room_id) REFERENCES rooms (room_id) );

43 Example Tables debug_table CREATE TABLE debug_table ( linecountNUMBER, debug_strVARCHAR2 (100) );

44 Example Tables exception_view CREATE VIEW exception_view AS SELECT exception exception_description, date_occurred FROM exception_table;

45 Example Tables log_table CREATE TABLE log_table ( codeNUMBER, messageVARCHAR2 (200), infoVARCHAR2 (100) );

46 Example Tables major_stats CREATE TABLE major_stats ( majorVARCHAR2 (30), total_creditsNUMBER, total_studentsNUMBER );

47 Example Tables registered_students CREATE TABLE registered_students ( student_idNUMBER (5)NOT NULL, departmentCHAR (3)NOT NULL, courseNUMBER (3)NOT NULL, gradeCHAR (1), CONSTRAINT rs_grade CHECK (grade IN ('A', 'B', 'C', 'D', 'E')), CONSTRAINT rs_student_id FOREIGN KEY (student_id) REFERENCES students (id), CONSTRAINT rs_department_course FOREIGN KEY (department, course) REFERENCES classes (department, course) );

48 Example Tables rooms CREATE TABLE rooms ( room_idNUMBER (5)PRIMARY KEY, buildingVARCHAR2 (15), room_numberNUMBER (4), number_seatsNUMBER (4), descriptionVARCHAR2 (50) );

49 Example Tables RS_audit CREATE TABLE RS_audit ( change_typeCHAR (1)NOT NULL, changed_byVARCHAR2 (8)NOT NULL, timestampDATENOT NULL, old_student_idNUMBER (5), old_departmentCHAR (3), old_courseNUMBER (3), old_gradeCHAR (1), new_student_idNUMBER (5), new_departmentCHAR (3), new_courseNUMBER (3), new_gradeCHAR (1) );

50 Example Tables student_sequence CREATE SEQUENCE student_sequence START WITH INCREMENT BY 1;

51 Example Tables students CREATE TABLE students ( id NUMBER(5) PRIMARY KEY, first_name VARCHAR2 (20), last_name VARCHAR2 (20), major VARCHAR2 (30), current_credits NUMBER(3) );

52 Example Tables temp_table CREATE TABLE temp_table ( num_colNUMBER, char_colVARCHAR2 (60) );

53 In Conclusion PL/SQL is a sophisticated programming language used to access an Oracle database Procedural constructs are integrated seamlessly with SQL, resulting in a structured, powerful language Combines flexibility of SQL with the configure ability of a 3GL