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Procedural Language for SQL
query a database and manipulate data
understand the goals of the PL/SQL cursus
explain the need for PL/SQL and the benefits
identify different types of PL/SQL blocks
use the different tools used during this cursus
Oracle Certifications
SQL Certified Expert (Introduction to SQL/Program with PL/SQL)
OCA (Introduction to SQL/Oracle Database Fundamental)
OCP (Oracle Database Fundamentals/Oracle on-Hand Course)
OCM (Oracle Database Certified Master Exam)
Reviews about SQL 10g
Introduction to SQL
DML(Data Manipulation Language) (select insert update delete merge)
DDL(Data Definition Language) (create alter drop rename truncate comment)
DCL(Data Control Language) (grant revoke)
TCL(Transaction Control) (commit rollback savepoint)
Retrieving data
select column, group_function from table where condition group by group_by_expression having group_condition order by column;
eg : select last_name, department_id from employees where department_id in (20,50) order by last_name ASC; (display the last name and department number of all employees in departments 20 or 50 in ascending alphabetical order by name)
selsct last_name, hire_date from employees where hire_date LIKE ‘%594‘; (displays the last name and hire date for all employees who were hired in 1994)
select last_name, salary, commission_pct from employees where commission_pct is not null order by salary DESC, commission_pct DESC;(display the last name, salary and commission for all employees who earn commissions. Sort data in descending order of salary and commissions)
select manager_id, MIN(salary) from employees where manager_id is not null group by manager_id having MIN(salary) > 6000 order by MIN(salary) desc; (to display the manager number and the salary of the lowest-paid employee for that manager, exclude anyone whose manager is not null, exclude any groups where the minimum salary is $6000 or less, sort the output in descending order of salary)
Manipulating data
insert into table column values value : add new rows to a table by using the insert statement
modify existing rows with the update statement : update table set column = value where condition;
delete from table where condition;
Creating objects
table : basic unit of storage; composed of rows
view : logically represents subsets of data from one or more table
sequense : generates numeric values
index : improves the performance of some queries
synonym : gives alternative names to objects
varchar2(size) : variable-length character data
char(size) : fixed-length character data
number(p,s) : variable-length numeric data
data : date and time values
long : variable-length character data (up to 2 GB)
clob : character data (up to 4 GB)
raw and long raw : raw binary data
blob : binary data(up to 4 GB)
bfile : binary data stored in an external file(up to 4 GB)
rowid : a base-64 number system representing the unique address of a row in its table
create table table column datatype;
PL/SQL curriculum
Communicating with a RDBMS using SQL
introduction to PL/SQL
provides a block structure for executable unit of code maintenance of code is made easier with such a well-defined structure.
provides procedural constructs such as variables, constants and types/ control structures such as conditional statements and loops/reusable program units that are written once and executed many times
benefits of PL/SQL
modularize program development
integration with Oracle tools
Portability
Exception handling
Different types of PL/SQL block
declare (optional) : variables, cursors, user-defined exceptions
begin (Mandatory) : SQL statements / PL/SQL statements
exception (optional) : actions to perform when errors occur
end (mandatory)
block types : anonymous / procedure / function
enable output in iSQL*PLUS with the command :
SET SERVEROUTPUT ON
use a predifined Oracle package and its procedure : DBMS_OUTPUT.PUT_LINE
EG : set serveroutput on
...
DBMS_OUTPUT.PUT_LINE(‘ The First Name of the Employee is ‘ || f_name);
Declaring variables in PL/SQL
Declare PL/SQL variables
Manipulate different types of variables
Make difference between variables and constants
Compare SQL and PL/SQL variables
PL/SQL variables
Presentation of PL/SQL Variables
Variables can be used for : temporary storage of data / manipulation of stored values / reusability
Identifiers are used for : naming a variable / providing a convention for variable names : must start with a letter/can include letters or numbers/can include special characters such as dollar sign, underscore, and pound sign/must limit the length to 30 characters/must not be reserved words
Variables are : declared and initialized in the declarative section / used and assigned new values in the executable section / passed as parameters to PL/SQL subprograms / used to hold the output of a PL/SQL subprogram
Declaring and initializing PL/SQL variables
syntax : identifier [CONSTRANT] datatype [not null] [ : | DEFAULT expr];
eg : declare emp_hiredate date; emp_deptno number(2) not null := 10; location varchar2(13) := ‘Atlanta‘; c_comm constraint number := 1400;
declaring and initializing PL/SQL variables :
SET SERVEROUTPUT ON
DECLARE
Myname VARCHAR2(20);
BEGIN
DBMS_OUTPUT.PUT_LINE(‘My name is : ‘|| Myname);
Myname := ‘John‘;
DBMS_OUTPUT.PUT_LINE(‘My name is : ‘|| Myname);
END;
/
SET SERVEROUTPUT ON
DECLARE
Myname VARCHAR2(20) := ‘John‘;
BEGIN
Myname := ‘Steven‘;
DBMS_OUTPUT.PUT_LINE(‘My name is : ‘|| Myname);
END;
/
Delimiters in string literals :
SET SERVEROUTPUT ON
DECLARE
event VARCHAR2(15);
BEGIN
event := q‘ !Father‘s day!‘;
DBMS_OUTPUT.PUT_LINE(‘3rd Sunday in June is : ‘||event);
event := q‘ [Mother‘s day]‘;
DBMS_OUTPUT.PUT_LINE(‘2nd Sunday in May is : ‘||event);
END;
/
Different types of PL/ SQL Variables
PL/SQL variables : Scalar (hold a single value) Composite Reference Large objects(LOB)
Non-PL/SQL variables : Bind variables
Guidelines for declaring and initializing PL/SQL variables :
follow naming conventions
use meaningful names for variables
initialize variables designated as NOT NULL and CONSTRAINT.
initialize variables with the assignment operator (:=) or the DEFAULT keyword (eg : Myname VARCHAR(20) := ‘John‘; Myname VARCHAR2(20) DEFAULT ‘John‘;)
declare on identifier per line for readability and code maintenance.
avoid using column names as identifiers
DECLARE
employee_id NUMBER(6);
BEGIN
SELECT employee_id
INTO employee_id
FROM employees
WHERE last_name = ‘Kochhar‘;
END;
/
with this syntax, only one row is selected at a time.
Base Scalar Data Types
CHAR [(fixed_length)]
VARCHAR2 (maximum_length)
LONG
LONG RAW
NUMBER [(precision, scale)]
BINARY_INTEGER
PLS_INTEGER
BOOLEAN
BINARY_FLOAT
BINARY_DOUBLE
DATE
TIMESTAMP
TIMESTAMP WITH TIME ZONE
TIMESTAMP WITH LOCAL TIME ZONE
INTERVAL YEAR TO MONTH
INTERVAL DAY TO SECOND
Declaring Boolean Variables
only the values TRUE, FALSE, and NULL can be assigned to a Boolean variable.
conditional expressions use logical operators AND, OR, and unary operator NOT to check the variable values.
the variables always yield TRUE, FALSE, or NULL
arithmetic, character, and date expressons can be used to return a Boolean value.
BINARY_FLOAT and BINARY_DOUBLE
representing floating point numbers in IEEE(Institute of Electrical and Electrnics Engineers) 754 format
offer better interoperability and operational speed
store values beyond the values that the data type NUMBER can store
offer benefits of closed arithmetic operations and transparent rounding
eg :
DECLARE
emp_job VARCHAR2(9);
count_loop BINARY_INTEGER := 0;
dept_total_sal NUMBER(9,2) := 0;
orderdate DATE := SYSDATE +7;
c_tax-rate CONSTRAINT NUMBER (3,2) := 8.25;
valid BOOLEAN NOT NULL := TRUE;
...
Composite Data Types
TABLE : to reference and manipulate collections of data as a whole object
RECORD : to treat related but dissimilar data as a logical unit
NESTED TABLE
VARRAY
LOB Data Type Variables(to store blocks of unstructured data (such as text, graphic images, video clips, and sound wave forms) up to 4 gigabytes in size)
BLOB(binary large object) : to store large unstructured or sturctured binary objects in the database
CLOB(character large object) : to store large blocks of character data in the database
BFILE(binary file) : to store large binary files outside the database (only a pointer to the BFILE is stored in the database)
NCLOB(national language character large object) : to store large blocks of single-byte or fixed-width multibyte NCHAR unicode data in the database
%TYPE Attribute is used to declare a variable according to : a database column definition / another declared variable and is prefixed with the database table and column / the name of the declared variable
Declaring variables with the %TYPE Attribute
Syntax: identifier table.column_name%type;
eg :
...
emp_name employees.last_name%type;
balance NUMBER(7,2);
min_balance balance%TYPE := 1000;
SQL variables
Bind variables
created in the environment
also called hosted variables
create with the VARIABLE keyword
used in SQL statements ans PL/SQL blocks
accessed even after the PL/SQL block is executed
reference with a preceding colon (":")
note : Bind variables are created in teh environment and not in the declarative section of a PL/SQL block. Variables declared in a PL/SQL block are available only when you execute the block.
create a bind variable in iSQL*Plus or in SQL*Plus
eg : VARIABLE return_code NUMBER
VARIABLE return_msg VARCHAR2(30)
use bind variables
eg :
VARIABLE result NUMBER
BEGIN
SELECT(SALARY*12) + NVL(COMMISSION_PCT,0) INTO :result
FROM employees WHERE employee_id = 144;
END;
/
PRINT result
Printing Bind Variables
eg :
VARIABLE emp_salary NUMBER
BEGIN
SELECT salary INTO :emp_salary
FROM employees WHERE employee_id = 178;
END;
/
PRINT emp_salary
SELECT first_name, last_name
FROM employees
WHERE salary=:emp_salary;
eg :
VARIABLE emp_salary NUMBER
SET AUTOPRINT ON
BEGIN
SELECT salary INTO :emp_salary
FROM employees WHERE employee_id = 178;
END;
/
note : use the command SET AUTOPRINT ON to automatically display the bind variables used in a successful PL/SQL block
Subsititution variables
used to get input at run time
referenced within a PL/SQL block with a preceding ampersand
used to avoid hard coding values that can be obtained at run time
eg :
VARIABLE emp_salary NUMBER
SET AUTOPRINT ON
DECLARE
empno NUMBER(6) :=&empno;
BEGIN
SELECT salary INTO :emp_salary
FROM employees WHERE employee_id = empno;
END;
/
Prompt for Substitution Variables
eg :
SET VERIFY OFF
VARIABLE emp_salary NUMBER
ACCEPT empno PROMPT ‘Please enter a valid employee number: ‘
SET AUTOPRINT ON
DECLARE
empno NUMBER(6) := &empno;
BEGIN
SELECT salary INTO :emp_salary GROM employees
WHERE employee_id = empno;
END;
/
User variables
Using DEFINE fro User Variable
eg :
SET VERIFY OFF
DEFINE lname = Urman
DECLARE
fname VARCHAR2(25);
BEGIN
SELECT first_name INTO fname FROM employees
WHERE last_name = ‘&lname‘;
END;
/
Executable section in PL/SQL
Write executable statements in a PL/SQL block
Write nested bocks
Define the scope and visibility of variables in the nested blocks
Qualify nested blocks with labels
Writing executable statements
Identify PL/SQL Block
Lexical units:
are building blocks of any PL/SQL block
are sequences of characters including letters, digits, tabs, spaces, returns, and symbols
can be classified as Identifiers / Delimiters / Literals / Comments
PL/SQL Block Syntax and Guidelines
Literals : Character and date literals must be enclosed in single quotation marks.
eg : name := ‘Henderson‘;
numbers can be simple values or scientific notation
note : a literal is an explicit numeric, character string, date or Boolean value that is not represented by an identifier. Character literals include all the printable characters in the PL/SQL character set : letters, numerals, spaces and special symbols. Numeric literals can be represented either by a simple value or by a scientific notation
Commenting Code
Prefix single-line comments with two dashes (--).
Place multiple-line comments between the symbol "/*" and "*/".
eg :
DECLARE
...
annual_sal NUMBER (9,2);
BEGIN -- Begin the executable section
/*Compute the annual salary based on the monthly salary input from the user */
annual_sal := monthly_sal *12;
END; -- This is the end of the block
/
SQL Functions in PL/SQL
Available in procedual statements :
Single-row number
Single-row character
Data type conversion
Date
Timestamp
GREATEST and LEAST
Miscellaneous functions
Not availabe in procedual statements
DECODE
Group functions
Get the length of a string :
desc_size INTEGER(5)
prod_description VARCHAR2(70) :=‘You can use this product with your radios for higher frequency‘;
-- get the length of the string in
-- prod_description
desc_size := LENGTH(PROD_DESCRIPTION);
Convert the employee name to lowercase:
emp_name := LOWER (emp_name)
Date Type Conversion
convert data to comparable data types
are of two types
implicit conversions
explicit conversions
xome conversion functions
some conversion functions
TO_CHAR
TO_DATE
TO_NUMBER
TO_TIMESTAMP
Data Type Conversion
date_of_joining DATE:= ‘02_Fev-2000‘;
date_of_joining DATE:= ‘February 02, 2000‘;
date_of_joining DATE:= TO_DATE(‘ February 02, 2000‘, ‘Month DD, YYYY‘);
Nested Block
PL/SQL blocks can be nested
an executable section(BEGIN ... END) can contain nested blocks
an exception section can contain blocks
eg :
DECLARE outer_variable VARCHAR2(20) := ‘GLOBAL BARAIBLE‘;
BEGIN
DECLARE
inner_variable VARCHAR2(20) := ‘LOCAL VARIABLE‘;
BEGIN
DBMS_OUTPUT.PUT_LINE(inner_variable);
DBMS_OUTPUT.PUT_LINE(outer_variable);
END;
DBMS_OUTPUT.PUT_LINE(outer_variable);
END;
/
Variable Scope and Visibility
eg :
DECLARE
father_name VARCHAR2(20) :=‘Patrick‘;
date_of_birth DATE:=‘20-April-1972‘;
BEGIN
DECLARE
child_name VARCHAR2(20) :=‘Mike‘;
date_of_birth DATE:= ‘12-Dec-2002‘;
BEGIN
DBMS_OUTPUT.PUT_LINE(‘Father‘ ‘s Name: ‘ || father_name);
DBMS_OUTPUT.PUT_LINE(‘Date of birth: ‘ || date_of_birth);
DBMS_OUTPUT.PUT_LINE(‘Child‘ ‘s name: ‘|| child_name);
END;
DBMS_OUTPUT.PUT_LINE(‘Date of Birth: ‘ || date_of_birth);
END;
/
Qualify an Identifier
<<outer>>
DECLARE
father_name VARCHAR2(20) :=‘Patrick‘;
date_of_birth Date:=‘20-Apr-1972‘;
BEGIN
DECLARE
child_name VARCHAR2(20) := ‘Mike‘;
date_of_birth DATE:=‘12-Dec-2002‘;
BEGIN
DBMS_OUTPUT.PUT_LINE(‘Father‘ ‘s Name: ‘ || father_name);
DBMS_OUTPUT.PUT_LINE(‘Date of Birth: ‘ || outer.date_of_birth);
DBMS_OUTPUT.PUT_LINE(‘Date of Birth: ‘ || date_of_birth);
END;
END;
/
Operators in PL/SQL
Logical
Arithmetic
Concatenation
Parentheses to control order of operations
Exponential operator
loop_count := loop_count +1; (Increment the counter for a loop)
good_sal := sal BETWEEN 50000 AND 150000; (Set the value of a Boolean flag)
valid := (empno IS NOT NULL); (Set the value of a Boolean flag.)
Programming Guidelines
Make code maintenance easier by :
Documenting code with comments
Developing a case convention for the code
Developing naming conventions for identifiers and other objects
Enhancing readability by indenting
Indenting Code
for clarity, indent each level of code
eg :
BEGIN
IF x=0 THEN
y :=1;
END IF;
END;
/
EG :
DECLARE
deptno NUMBER(4);
location_id NUMBER(4);
BEGIN
SELECT department_id;
local_id
INTO deptno, location_id
FROM departments
WHERE department_name = ‘Sales‘;
...
END;
/
Labs: Executable section in PL/SQL
04 Cursors, logical structures and composite data types
Use SQL statements in PL/SQL
Use SQL cursors in PL/SQL
Identify the uses and types of control structures
Construct and identify different loop statements
Create user-defined PL/SQL records
Create an INDEX BY table of records
Declare and control explicit cursors
Displaying data from multiple tables
Using subqueries to solve queries
Using the set operators
Interacting with the Oracle server
SQL Statements in PL/SQL
Retrive a row from the database by using the SELECT command.
Make changes to rows in the database by using DML commands
Control a transaction with the COMMIT, ROLLBACK, or SAVEPOINT command.
SELECT Statements in PL/SQL
Retrieve data from the database with a SELECT statement
syntax :
SELECT select_list
INTO {variable_name [, variable_name]...| record_name}
FROM table
[WHERE condition];
The INTO clause is required
Queries must return only one row
eg :
SET SERVEROUTPUT ON
DECLARE
fname VARCHAR2(25);
BEGIN
SELECT first_name INTO fname
FROM employees WHERE employee_id=200;
DBMS_OUTPUT.PUT_LINE(‘ First Name is : ‘ | | fname);
END;
/
Retrieving Data in PL/SQL
Retrieve the hire_date and the salary for the specified employee
eg :
DECLARE
emp_hiredate employees.hire_date%TYPE;
emp_salary employees.salary%TYPE;
BEGIN
SELECT hire_date, salary
INTO emp_hiredate, emp_salary
FROM employees
WHERE employee_id = 100;
END;
/
Return the sum of the salaries for all the employees in the specified department
eg :
SET SERVEROUTPUT ON
DECLARE
sum_sal NUMBER(10,2);
deptno NUMBER NOT NULL := 60;
BEGIN
SELECT SUM(salary) -- group function
INTO sum_sal FROM employees
WHERE department_id = deptno;
DBMS_OUTPUT.PUT_LINE (‘The sum of salary is ‘ | | sum_sal);
END;
/
Naming Conventions
eg :
DECLARE
hire_date employees.hire%TYPE;
sysdate hire_data%TYPE;
employee_id employees.employee_id%TYPE := 176;
BEGIN
SELECT hire_date,sysdate
INTO hire_date, sysdate
FROM employees
WHERE employee_id = employee_id;
END;
/
Naming Conventions
Use a naming convention to avoid ambiguity in the WHERE clause.
Avoid using database column names as identifiers
Syntax errors can arise because PL/SQL checks the database first for a column in the table.
The names of local variables and formal parameters take precedence over the names of database tables
The names of database table columns take precedence over the names of local variables.
Data Manipulation in PL/SQL
Make changes to database tables by using DML commands :
INSERT
Inserting Data
Add new employee information to the EMPLOYEES table
eg :
BEGIN
INSERT INTO employees (employee_id, first_name, last_name, email, hire_date, job_id, salary) VALUES (employees_seq.NEXTVAL, "Ruth‘, ‘Cores‘, ‘RCORES‘, sysdate, ‘AD_ASST‘, 4000);
END;
/
UPDATE
Updating data
Increase the salary of all employees who are stock clerks
eg :
DECLARE
sal_increase employees.salary%TYPE := 800;
BEGIN
UPDATE employees
SET salary = salary + sal_increase
WHERE job_id = ‘ST_CLERK‘;
END;
/
DELETE
Deleting data
Delete rows that belong to department 10 from the employees table.
eg :
DECLARE
deptno employees.department_idTYPE := 10;
BEGIN
DELETE FROM employees
WHERE department_id = deptno;
END;
/
MERGE
Merging rows
Insert or update rows in the copy_emp table to match the employees table.
DECLARE
empno employees.employee_id%TYPE := 100;
BEGIN
MERGE INTO copy_emp c USING employees e ON (e.employee_id = empno) WHEN MATCHED THEN UPDATE SET c.first_name = e.first_name, c.last_name = e.last_name, c.email = e.email, ... WHEN NOT MATCHED THEN INSERT VALUES (e.employee_id, e.first_name, e.last_name, ... e.department_id);
END;
SQL Cursors
a cursor is a pointer to the private memory area allocated by the Oracle server.
There are two types of cursors :
Implicit cursors : created and manged internally by the Oracle server to process SQL statements
Explicit cursors : explicitly declared by the programmer
SQL cursor attributes for implicit cursots
using SQL cursor attributes, you can test the outcome of your SQL statements
SQL%FOUND : Boolean attribute that evaluates to TRUE if the recent SQL statement returne at least on row.
SQL%NORFOUND :Boolean attribute that evaluates to TRUE if the most recent SQL statement did not return even one row.
SQL%ROWCOUNT :An integer value that represents number of rows affected by the most recent SQL statement.
Delete rows that have the specified employee ID from the employees table. Print the number of rows deleted.
eg :
VARIABLE rows_deleted VARCHAR2(30)
DECLARE
empno employees.employee_id%TYPE := 176;
BEGIN
DELETE FROM employees
WHERE employee_id = empno;
: rows_deleted := (SQL%ROWCOUNT || ‘ row deleted.‘);
END;
/
Writing conrtol structures
IF Statements
syntax :
IF condition THEN statements;
[ELSIF condition THEN statements;]
[ELSE statements;]
END IF;
eg :
DECLARE myage number := 31;
BEGIN IF myage <11 THEN DBMS_OUTPUT.PUT_LINE(‘ I am a child ‘);
END IF;
END;
/
Working with composite data types
Using explicit cursors
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原文地址：http://www.cnblogs.com/jilili/p/4314500.html
