SQL*PLUS, PLSQL and SQLLDR Ali Obaidi

SQL Advantages High level – Builds on relational algebra and calculus – Powerful operations – Enables automatic optimization Table oriented – Direct representation and manipulation as bags of rows Standardized – ANSI standards – Compatibility across vendors Gateway to other languages – Embeddings in 3GL languages (e.g. C++) – Client software via ODBC, JDBC

PL/SQL A Procedural Extension To SQL – Procedural, statement oriented –Blocks, declarations, assignable variables, conditionals, iterations, exceptions – Subprograms –Procedures, functions – Packages –With specification separate from body – Composite datatypes –Rows, cursors, records (structs), tables (arrays)

Achievements Modular, Reusable Database Manipulation and Maintenance Code Stored objects –Procedures, functions packages External procedures –PL/SQL code invoked from 3GL languages Triggers Stored procedures invoked by insert, delete, update Crucial for integrity maintenance

Using PL/SQL From SQL*Plus Execute the following to enable printing –set serveroutput on Defining procedures –Since procedures, functions and packages are objects, use : create Do a drop first –create or replace –Type in source code, execute by single line containing “/” Can also input from source file –start Examine syntax errors by –show errors

Example SQL> declare i integer; j integer; begin i := 0; for j in loop i := i+j; end loop; dbms_output.put_line(i); end; /

Cursors Cursors allow embedded SQL statements –Result is a set (table) in a temporary work area Cursor name permits iterative manipulation of rows Two varieties of cursors –Implicit Quick to write For simple iteration of resulting row set –Explicit More detailed to write Permit more advanced manipulations

Example SQL> create or replace procedure sumsalary IS cursor c1 is select * from employee; salsum integer; begin salsum := 0; for emp_rec in c1 loop salsum := salsum + emp_rec.salary; end loop; dbms_output.put_line('Salary sum: ' || salsum); end; 13 / SQL> exec sumsalary Salary sum:

Explicit Cursor Operations Declare –Introduces cursor object, bound to SQL statement OPEN –Constructs temporary table FETCH –Accesses next row Tests – %FOUND, %NOTFOUND, %ROWCOUNT, %ISOPEN CLOSE –Releases temporary table and associated working data

SQL> DECLARE CURSOR c1(min_salary integer) IS SELECT name FROM employee WHERE salary > min_salary; PROCEDURE count_salaries(m_s integer) IS emp_rec c1%ROWTYPE; how_many integer := 0; BEGIN OPEN c1(m_s); FETCH c1 INTO emp_rec; WHILE c1%FOUND LOOP how_many := how_many + 1; FETCH c1 INTO emp_rec; END LOOP; dbms_output.put_line(how_many || ' employees have salary > '17 || m_s); CLOSE c1; END; BEGIN count_salaries(40000); count_salaries(60000); END; / 5 employees have salary > employees have salary > 60000

Relational Data Model  Defined by Edgar Codd in 1970  Considered ingenious but impractical  Conceptually simple  Relational DB is perceived as a collection of tables  Provides SQL, a 4GL

Functions In PL/SQL SQL> create or replace function f(i in integer) return integer IS begin return i*i; end; / Function created. SQL> exec dbms_output.put_line(f(13)); 169