ISYS 365 – SQL*Plus Environment

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

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

Command Line Editor list or list # change del 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

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

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

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 (set the width of the column Item to 18 characters column Rate format 90.99 zero tells SQL*Plus to pad the number with a zero (if necessary) 999,999,999 99.90 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

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 90.99 Use nines and zeros to specify the numeric pattern Examples: (a) 999,999,999 (b) 99.90 COLUMN Salary FORMAT $999,999.99 See “numeric formatting” in Oracle Complete Reference

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

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

Break on Example BREAK ON DEPARTMENT_ID SKIP PAGE ON JOB_ID SKIP 1 ON SALARY SKIP 1 SELECT DEPARTMENT_ID, JOB_ID, SALARY, LAST_NAME FROM EMP_DETAILS_VIEW WHERE SALARY > 12000 ORDER BY DEPARTMENT_ID, JOB_ID, SALARY, LAST_NAME; All rows with the same DEPARTMENT_ID print together on one page, and within that page all rows with the same JOB_ID print in groups. Within each group of jobs, those jobs with the same SALARY print in groups. Breaks in LAST_NAME cause no action because LAST_NAME does not appear in the BREAK command.

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

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)

Oracle spool tips The SPOOL command causes SQL*Plus to write the results to a file on the operating system. SQL> spool myfile.lst SQL> spool off; if you spool out a file that does not exist, SQL*Plus creates a new file.  SQL*Plus replaces the existing file if the file name already exists.  In Oracle 10g, the SPOOL command has a new APPEND option.  Now, you can append new SQL*Plus output in an existing file. 

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

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

Useful System Tables User_Constraints User_Cons_Columns Useful fields: constraint_name, table_name, constraint_type constraint_type: C (Check Constraint on a table), P (Primary Key), R (Referential Integrity) & U (Unique) User_Cons_Columns Useful fields: constraint_name, column_name, position SELECT column_name FROM user_cons_columns WHERE constraint_name=‘SYS_C0008791’; Retrieving constraints defined by the user WHERE CONSTRAINT_NAME NOT LIKE '%SYS%';

Useful System Tables user_sequences user_errors 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

Creating a Sequence: Example CREATE SEQUENCE customers_seq START WITH 1000 INCREMENT BY 1

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

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

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

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; / %NOTFOUND: this attribute yields the number of rows affected by am INSERT, UPDDATE or DELETE statement affected no rows, or a SELECT INTO statement returned no rows. Otherwise it yields FALSE

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

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

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

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

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)

File Error.sql Illustrates an exception handler 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; /

SQLCODE, SQLERRM SQLCODE is only useful in an exception handler. Othside a handler SQLCODE always returns 0, it let you identify which internal exception was raised. You can’t use SQLCODE directly in a SQL statement. Assign the value of SQLCODE to a local variable first The function SQLERRM returns the error message associated with its error-number argument. If the argument is omitted, it returns the error message associated with the current value of SQLCODE

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

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

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; /

File NumericLoop.sql Demonstrates a numeric FOR loop BEGIN FOR v_LoopCounter IN 1..50 LOOP INSERT INTO temp_table (num_col) VALUES (v_LoopCounter); END LOOP; END; /

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

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;

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

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 VALUES ('There are only a few students registered'); ELSIF v_TotalStudents < 10 THEN VALUES ('There are a little more students registered'); ELSE VALUES ('There are many students registered'); END IF; END; /

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; /

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

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

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

File tables.sql PROMPT student_sequence... DROP SEQUENCE student_sequence; CREATE SEQUENCE student_sequence START WITH 10000 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) ); …

Example Tables classes CREATE TABLE classes ( department CHAR (3), course NUMBER (3), description VARCHAR2 (2000), max_students NUMBER (3), current_students NUMBER (3), num_credits NUMBER (1), room_id NUMBER (5), CONSTRAINT classes_department_course PRIMARY KEY (department, course), CONSTRAINT classes_room_id FOREIGN KEY (room_id) REFERENCES rooms (room_id) );

Example Tables debug_table CREATE TABLE debug_table ( linecount NUMBER, debug_str VARCHAR2 (100) );

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

Example Tables log_table CREATE TABLE log_table ( code NUMBER, message VARCHAR2 (200), info VARCHAR2 (100) );

Example Tables major_stats CREATE TABLE major_stats ( major VARCHAR2 (30), total_credits NUMBER, total_students NUMBER );

Example Tables registered_students CREATE TABLE registered_students ( student_id NUMBER (5) NOT NULL, department CHAR (3) NOT NULL, course NUMBER (3) NOT NULL, grade CHAR (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) );

Example Tables rooms CREATE TABLE rooms ( room_id NUMBER (5) PRIMARY KEY, building VARCHAR2 (15), room_number NUMBER (4), number_seats NUMBER (4), description VARCHAR2 (50) );

Example Tables RS_audit CREATE TABLE RS_audit ( change_type CHAR (1) NOT NULL, changed_by VARCHAR2 (8) NOT NULL, timestamp DATE NOT NULL, old_student_id NUMBER (5), old_department CHAR (3), old_course NUMBER (3), old_grade CHAR (1), new_student_id NUMBER (5), new_department CHAR (3), new_course NUMBER (3), new_grade CHAR (1) );

Example Tables student_sequence CREATE SEQUENCE student_sequence START WITH 10000 INCREMENT BY 1;

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) );

Example Tables temp_table CREATE TABLE temp_table ( num_col NUMBER, char_col VARCHAR2 (60) );

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