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Using Oracle PL/SQL
• PL/SQL
stands for Procedural Language/SQL.
• PL/SQL extends SQL by adding constructs found in procedural languages, resulting in a structural language that is more powerful than SQL.
• The basic unit in PL/SQL is a block. All PL/SQL programs are made up of blocks
block structureDECLARE
/* Declarative section: variables, types, and local subprograms. */
BEGIN
/* Executable section: procedural and SQL statements go here. */
/* This is the only section of the block that is required. */
EXCEPTION
/* Exception handling section: error handling statements go here. */
END;
Execute a PL/SQL
• To execute a PL/SQL program
must follow the program text itself by– A line with a single dot ("."), and then – A line with run;
• with Oracle SQL programs, we can invoke a PL/SQL program by typing it in sqlplus
Variables and Types
• Type– One of the types used by SQL for database colum
ns – A generic type used in PL/SQL such as NUMBER – Declared to be the same as the type of some data
base column • E.G.
DECLARE
price NUMBER;
myName VARCHAR(20);
Variables and Types
• %TYPE operator DECLARE
myName Emp.name%TYPE;
• %ROWTYPE operator DECLARE
EmpTuple Emp%ROWTYPE;
Variables and Types
• ":=" operator
• e.g DECLARE
a NUMBER := 3;
BEGIN
a := a + 1;
END;
.
run;
Simple Programs in PL/SQL
• Plain SQL CREATE TABLE T1(
e INTEGER,
f INTEGER
);
DELETE FROM T1;
INSERT INTO T1 VALUES(1, 3);
INSERT INTO T1 VALUES(2, 4);
1 3
2 4
e fT1
Simple Programs in PL/SQL
• PL/SQL programDECLARE
a NUMBER;
b NUMBER;
BEGIN
SELECT e,f INTO :a,:b FROM T1 WHERE e>1;
INSERT INTO T1 VALUES(:b,:a);
END;
.
run;
1 3
2 4
e fT1
4 2
Control Flow in PL/SQL
• IF statementIF <condition_1> THEN ...
ELSIF <condition_2> THEN ...
... ...
ELSIF <condition_n> THEN ...
ELSE ...
END IF;
Control Flow in PL/SQL
• E.g.DECLARE
a NUMBER;
b NUMBER;
BEGIN
SELECT e,f INTO :a, :b FROM T1 WHERE e>1;
IF b=1 THEN
INSERT INTO T1 VALUES(:b,:a);
ELSE
INSERT INTO T1 VALUES(:b+10,:a+10);
END IF;
END;
.
run;
Control Flow in PL/SQL
• Loops : LOOP
<loop_body> /* A list of statements. */
END LOOP;
• EXIT EXIT WHEN <condition>;
• E.G.DECLARE
i NUMBER := 1;
BEGIN
LOOP
INSERT INTO T1 VALUES(:i,:i);
i := i+1;
EXIT WHEN i>100;
END LOOP;
END;
.
run;
Control Flow in PL/SQL
• WHILE loop WHILE <condition> LOOP
<loop_body>
END LOOP;
• FOR loop FOR <var> IN <start>..<finish> LOOP
<loop_body>
END LOOP;
DECLARE x NUMBER := 100;BEGIN FOR i IN 1..10 LOOP IF MOD(i,2) = 0 THEN -- i is even INSERT INTO temp VALUES (i,: x, 'i is even'); ELSE INSERT INTO temp VALUES (i, :x, 'i is odd'); END IF;
x := x + 100; END LOOP; COMMIT;END;.run
DECLARE acct_balance NUMBER(11,2);
acct CONSTANT NUMBER(4) := 3;
debit_amt CONSTANT NUMBER(5,2) := 500.00;
BEGIN SELECT bal INTO :acct_balance FROM accounts
WHERE account_id = :acct
FOR UPDATE OF bal;
IF acct_balance >= debit_amt THEN UPDATE accounts SET bal = bal - :debit_amt
WHERE account_id = :acct;
ELSE INSERT INTO temp VALUES
(:acct, :acct_balance, 'Insufficient funds');
-- insert account, current balance, and message
END IF;
COMMIT;
END;
DECLARE salary emp.sal%TYPE; mgr_num emp.mgr%TYPE; last_name emp.ename%TYPE; starting_empno CONSTANT NUMBER(4) := 7902;
BEGIN SELECT sal, mgr INTO :salary, :mgr_num FROM emp WHERE empno = :starting_empno;
WHILE salary < 4000 LOOP SELECT sal, mgr, ename INTO :salary, :mgr_num, :last_name FROM emp WHERE empno = :mgr_num;
END LOOP;
INSERT INTO temp VALUES (NULL, :salary, :last_name); COMMIT;
END;
Cursors
• DefinitionCURSOR T1 Cursor IS
SELECT e, f
FROM T1
WHERE e < f;
1) DECLARE /* Output variables to hold the result of the query: */ 2) a T1.e%TYPE; 3) b T1.f%TYPE; /* Cursor declaration: line 4-8*/ 4) BEGIN 9) OPEN T1Cursor;10) LOOP /* Retrieve each row of the result of the above query into PL/SQL variables: */11) FETCH T1Cursor INTO a, b; /* If there are no more rows to fetch, exit the loop: */12) EXIT WHEN T1Cursor%NOTFOUND; /* Insert the reverse tuple: */13) INSERT INTO T1 VALUES(b, a);14) END LOOP; /* Free cursor used by the query. */15) CLOSE T1Cursor;16) END;17) .18) run;
DECLARE CURSOR my_cursor IS SELECT sal + NVL(comm, 0) wages, ename FROM emp; my_rec my_cursor%ROWTYPE;
BEGIN OPEN my_cursor;
LOOP FETCH my_cursor INTO :my_rec;
EXIT WHEN my_cursor% NOTFOUND; IF my_rec.wages > 2000 THEN INSERT INTO temp VALUES (NULL, my_rec.wages, my_rec.ename);
END IF; END LOOP; CLOSE my_cursor;
END;
DECLARE CURSOR num1_cur IS SELECT num FROM num1_tab ORDER BY sequence; CURSOR num2_cur IS SELECT num FROM num2_tab ORDER BY sequence; num1 num1_tab.num%TYPE; num2 num2_tab.num%TYPE; pair_num NUMBER := 0;
BEGIN OPEN num1_cur; OPEN num2_cur;
LOOP -- loop through the two tables and get -- pairs of numbers FETCH num1_cur INTO :num1; FETCH num2_cur INTO :num2; EXIT WHEN (num1_cur%NOTFOUND) OR (num2_cur%NOTFOUND); pair_num := pair_num + 1; INSERT INTO sum_tab VALUES (pair_num, num1 + num2);
END LOOP; CLOSE num1_cur; CLOSE num2_cur;
END;
DECLARE CURSOR c1 is SELECT ename, empno, sal FROM emp ORDER BY sal DESC; -- start with highest-paid employee my_ename CHAR(10); my_empno NUMBER(4); my_sal NUMBER(7,2);
BEGIN OPEN c1;
LOOP FETCH c1 INTO :my_ename, :my_empno, :my_sal; EXIT WHEN (c1%ROWCOUNT > 5) OR (c1%NOTFOUND); INSERT INTO temp VALUES (my_sal, my_empno, my_ename); COMMIT;
END LOOP; CLOSE c1;
END;
DECLARE num1 data_table.n1%TYPE; -- Declare variables num2 data_table.n2%TYPE; -- to be of same type as num3 data_table.n3%TYPE; -- database columns result temp.num_col1%TYPE; CURSOR c1 IS SELECT n1, n2, n3 FROM data_table WHERE exper_num = 1;
BEGIN OPEN c1;
LOOP FETCH c1 INTO :num1, :num2, :num3;
EXIT WHEN c1%NOTFOUND; -- the c1%NOTFOUND condition evaluates -- to TRUE when FETCH finds no more rows /* calculate and store the results */ result := num2/(num1 + num3); INSERT INTO temp VALUES (result, NULL, NULL);
END LOOP; CLOSE c1; COMMIT;
END;
I/O Control
• DBMS_OUTPUT.NEW_LINE();
• DBMS_OUTPUT.PUT_LINE();
• DBMS_OUTPUT.PUT();
I/O Example
BEGIN /* Get Current User Name */ SELECT username INTO :l_current_user FROM USER_USERS; DBMS_OUTPUT.NEW_LINE(); DBMS_OUTPUT.PUT('Connect As '||l_current_user); DBMS_OUTPUT.PUT(' And Add Details For '||RTRIM(Empname)); DBMS_OUTPUT.PUT_LINE(' having Id '||RTRIM(empid));
INSERT INTO Employee_table VALUES(Empid, Empname, Empadd, Deptcd,
Grade, SYSDATE);
/* Increment Department strength */ Increment_Dept_Strength(Deptcd); END Insert_Emp_Details;
Logging In to Oracle
• log in to Oracle by typing:
sqlplus <yourName>• Changing Your Password
alter user <yourName identified by <newPassword;
Quitting sqlplus
• To leave sqlplus, type
quit;
Executing SQL From a File
• Executing SQL From a Filesqlplus <yourName/<yourPassword @<fileName
• e.g.
sqlplus sally/etaoinshrdlu @foo
OR
@foo.sql
Editing Commands
• L lists the command buffer, and makes the last line in the buffer the "current" line
• L n prints line n of the command buffer, and makes line n the current line
• L m n prints lines m through n, and makes line n the current line
Editing Commands - cont.
• I enters a mode that allows you to input text following the current line; you must terminate the sequence of new lines with a pair of "returns"
• C /old/new replaces the text "old" by "new" in the current line
• A text appends "text" to the end of the current line
• DEL deletes the current line
• Exercises
4.5 using PL/SQL
