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C20.0046: Database
Management Systems
Lecture #19
M.P. Johnson
Stern School of Business, NYU
Spring, 2005
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
1
Homework

Project part 3 due today
Project part 4 up soon…

Topic: populating your tables with data



Using MySQL’s bulk loader
Can get errors parsing

Start early!
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
2
NYU Infrastructure News

The Oracle client should be working as usual
again

Can run sqlplus and Pro*C programs without
touching TWO_TASK
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
3
Agenda: Programming for SQL
Embedded SQL


Pro*C, SQLJ
CLI

SQL/CLI in C

JDBC in Java

DBI/DBDs in Perl, PHP
Stored Procedures:




PL/SQL, Triggers
MySQL Bulk Loader
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
4
Goals
Have more confidence in writing
scripts/functions/procedures
1.

Be able to define a simple trigger
2.

3.
Be able to respond to ftn/proc errors
So code executes at the right time
Understand how to load a text file of records
into MySQL
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
5
PL/SQL

“Procedural Language for SQL”

Oracle’s language for stored procedures

Simple, interpreted, procedural language

But Pascal-like:




BEGIN END, not { }
AND OR, not && ||
vars defined at top of procedre
how return works
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
6
Hello, World

Try again…
SET SERVEROUTPUT ON
BEGIN
-- print out message
DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL');
END;
/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
7
Example procedure

Define the procedure:
CREATE PROCEDURE testProcedure AS
BEGIN
INSERT INTO Student VALUES (5, ‘Godel');
END;

Now we can call it:
EXEC testProcedure
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
8
Procedure I/O example

A procedure to take a beer and price and add
it to Joe's menu: Sells(bar, beer, price)
CREATE PROCEDURE izzyMenu(
b IN Sells.beer%TYPE,
p IN Sells.price%TYPE) AS
BEGIN
INSERT INTO Sells
VALUES(‘Izzy’’s', b, p);
END;
/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
9
Function example
CREATE OR REPLACE FUNCTION maxval(a
IN int, b IN int) RETURN int AS
BEGIN
IF a > b THEN RETURN a;
ELSE RETURN b;
END IF;
END maxval;
INSERT INTO R VALUES(“abc”, maxval(5,10));

http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/maxval.sql
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
10
http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/wordcount.sql
CREATE OR REPLACE FUNCTION wordcount (str IN
VARCHAR2)
RETURN PLS_INTEGER AS
/* words PLS_INTEGER := 0; ***Commented out for
intentional error*** */
len PLS_INTEGER := NVL(LENGTH(str),0);
inside_a_word BOOLEAN;
BEGIN
FOR i IN 1..len + 1 LOOP
IF ASCII(SUBSTR(str, i, 1)) < 33 OR i > len
THEN
IF inside_a_word
THEN
words := words + 1;
inside_a_word := FALSE;
END IF;
ELSE
inside_a_word := TRUE;
END IF;
END LOOP;
RETURN words;
END; M.P. Johnson, DBMS, Stern/NYU, Spring 2005
Word
count
program
11
Getting errors

Simple says:
Warning: Function created with compilation
errors.


To get actual errors, say SHOW ERR(ORS)
Can also get errors per object:
SQL> show errors function wordcount


Warning: must get object type right!
Can also look at user_errors tbl directly
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
12
Stored ftns & procs persist

Once a function or procedure is created, it
persists until it’s dropped
CREATE OR REPLACE FUNCTION …

Stored procs are stored in the DB itself

In user_procedures in Oracle
SELECT object_name from user_procedures;

Also, can describe ftns and procs:
SQL> describe wordcount
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
13
Calling functions and procedures

Procedures can simple executed, ftns can’t

How to just call a ftn?
Can use dbms_output, as seen
Can also select the ftn value from dual
1.
2.
SQL> select(wordcount(‘hi there’) from dual;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
14
Programs and rights


By default, only the creator of a program may
run it (apart from the admin)
If others should run, must GRANT them
permission:
SQL> GRANT EXECUTE ON wordcount TO george;

Permissions can be revoked:
SQL> REVOKE EXECUTE FROM wordcount TO george;

Can also grant to particular roles or everyone:
SQL> GRANT EXECUTE ON wordcount TO everyone;

Wider/narrower grant ops are independent…
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
15
Branching




IF–THEN statements use THEN
Must end with END IF
Use ELSIF in place of ELSE IF
Example:

IF <condition> THEN
<statement(s)>
ELSIF
<statement(s)>
END IF;
http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/maxval.sql
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
16
More ifs
IF <condition>
ELSE
END IF;
IF <expression>
ELSEIF <expression>
ELSE
END IF;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
17
Multiple elsifs

An if statement can have multiple elseifs:
IF salary >= 10000 AND salary <= 20000
THEN give_bonus(employee_id, 1500);
ELSIF salary > 20000 AND salary <= 40000
THEN give_bonus(employee_id, 1000);
ELSIF salary > 40000
THEN give_bonus(employee_id, 400);
END IF;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
18
Loop example
DECLARE
i NUMBER := 1;
BEGIN
LOOP
INSERT INTO T1
VALUES(i,i);
i := i+1;
EXIT WHEN i>100;
END LOOP;
END;
/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
19
More loops


Infinite loop:
while loop:
LOOP
executable_statements;
END LOOP;
WHILE condition
LOOP
executable_statements;
END LOOP;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
20
For loops

Integer for loop:
FOR for_index IN low_value .. high_value
LOOP
executable_statements;
END LOOP;

Cursor for loop:
FOR record_index IN my_cursor
LOOP
executable_statements;
END LOOP;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
21
For loop example
FOR my-rec IN my-cursor LOOP
…
END LOOP;

Example:

http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/for.sql
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
22
PL/SQL v. SQL

There are some things SQL can’t do (e.g., factorial), but some
problems can be solved in both
DECLARE
CURSOR checked_out_cur IS
SELECT pet_id, name, checkout_date
FROM occupancy WHERE checkout_date IS NOT NULL;
BEGIN
FOR checked_out_rec IN checked_out_cur
LOOP
INSERT INTO occupancy_history (pet_id, name, checkout_date)
VALUES (checked_out_rec.pet_id, checked_out_rec.name,
checked_out_rec.checkout_date);
DELETE FROM occupancy WHERE pet_id =
checked_out_rec.pet_id;
END LOOP;
23
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
END;
PL/SQL v. SQL

The same thing can be done w/o a cursor:
BEGIN
INSERT INTO occupancy_history (pet_id, NAME, checkout_date)
SELECT pet_id, NAME, checkout_date
FROM occupancy WHERE checkout_date IS NOT NULL;
DELETE FROM occupancy WHERE checkout_date IS NOT NULL;
END;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
24
Dynamic PL/SQL

Saw “dynamic SQL” in the cases of Pro*C
and JDBC


Ability to run ad-hoc (non-hard-coded) SQL in
programs/scripts
Can also do this in PL/SQL
EXECUTE IMMEDIATE <string>;

The string can be passed in, created from
concatenation, etc.
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
25
Dynamic PL/SQL

E.g.: write function to return number rows in
an arbitrary table
CREATE OR REPLACE FUNCTION rowCount (
tabname IN VARCHAR2) return integer as
retval integer;
begin
execute immediate 'select count(*) from ' || tabname into
retval;
return retval;
end;
/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
26
Dynamic PL/SQL for DDL

Ordinarily can’t do DDL in PL/SQL
But you can in dynamic PL/SQL

Here’s an e.g.:

CREATE OR REPLACE procedure
dropproc(procname in varchar2) as
begin
execute immediate 'drop procedure ' || procname;
end;
/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
27
More on PL/SQL

O’Reilly’s Oracle PL/SQL Programming:



PL/SQL Reference & Tutorial:


http://www.ilook.fsnet.co.uk/ora_sql/sqlmain2.htm
Introduction to PL/SQL:


http://www.unix.org.ua/orelly/oracle/prog2/
This lecture somewhat follows 3rd edition of this book
http://www.geocities.com/cliktoprogram/plsql/introduction.html
Oracle FAQ's Script and Code Exchange:

http://www.orafaq.com/scripts/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
28
Live examples

Factorial function:


Converting between bases:


http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/
fact.sql
http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/
numsys.sql
Directory of examples:

http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
29
New topic: Triggers

PL/SQL programs that run automatically (are
“triggered”) when a certain event occurs

E.g.: on insert to some table
On system start-up
On delete from table




Big benefit: need not be called explicitly
However row in table x is deleted, the trigger
gets called
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
30
Trigger events


Trigger code may be “triggered” by many kinds of
events:
Oracle start-up/shut-down


Data updates:





Triggers may replace initialization scripts
Delete: maybe delete related rows
Inserts
Updates: maybe make other rows consistent
Delete: maybe prevent
DDL statements

Log creation of all objects, e.g.
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
31
Triggers

Constraints state what must remain true

DBMS decides when to check

Triggers are instructions to perform at explicitly
specified times

Three aspects:




An event (e.g., update to an attribute)
A condition (e.g., a test of that update value)
An action (the trigger’s effect) (deletion, update, insertion)
When the event occurs, DBMS checks the
constraint, and if it is satisfied, performs the action
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
32
DML trigger options

The trigger may be:



The trigger may run




Statement-level (e.g., a DELETE WHERE statement) or
Row-level (e.g., for each row deleted)
BEFORE
AFTER or
INSTEAD OF the statement (in Oracle, not in others)
It may be triggered by



INSERTs
UPDATEs
DELETEs
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
33
Trigger form
CREATE [OR REPLACE] TRIGGER trigger
name
{BEFORE | AFTER | INSTEAD OF}
{INSERT | DELETE | UPDATE | UPDATE OF
column list} ON table name
[FOR EACH ROW]
[WHEN (...)]
[DECLARE ... ]
BEGIN
... executable statements ...
[EXCEPTION ... ]
END [trigger name];
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
34
Skip to: Extended auditing example
Trigger type examples

First run copy_tables.sql
1.
statement_vs_row.sql

INSERT INTO to_table SELECT * FROM from_table;
before_vs_after.sql
2.

INSERT INTO to_table SELECT * FROM from_table;
one_trigger_per_type.sql
3.

INSERT INTO to_table VALUES (1);
UPDATE to_table SET col1 = 10;
DELETE to_table;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
35
DML Trigger e.g.
CREATE OR REPLACE TRIGGER
validate_employee_changes
BEFORE INSERT OR UPDATE
ON employee
FOR EACH ROW
BEGIN
check_age (:NEW.date_of_birth);
check_resume (:NEW.resume);
END;

Q: Why is this (maybe) better than client-side
validation?
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
36
Triggers with WHEN
CREATE OR REPLACE TRIGGER check_raise
AFTER UPDATE OF salary, commission
ON employee
FOR EACH ROW
WHEN ((OLD.salary != NEW.salary OR
(OLD.salary IS NULL AND NEW.salary IS NULL))
OR (OLD.commission != NEW.commission OR
(OLD.commission IS NULL AND NEW.commission IS NULL)))
BEGIN
...
END;

NB: WHEN applies only to row-level triggers
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
37
Triggers with WHEN



Remember: WHEN applies only to row-levels
Parentheses are required
Can only call built-in functions in when

Packages like DBMS_OUTPUT are not allowed
CREATE OR REPLACE TRIGGER
valid_when_clause
BEFORE INSERT ON frame
FOR EACH ROW
WHEN ( TO_CHAR(SYSDATE,'HH24')
BETWEEN 9 AND 17 )
...
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
38
Multiple DML actions


DML actions may be ORed together
To find actual
action, check:



INSERTING
DELETING
UPDATING
CREATE OR REPLACE TRIGGER
three_for_the_price_of_one
BEFORE DELETE OR INSERT OR UPDATE
ON account_transaction
FOR EACH ROW
BEGIN
IF INSERTING
THEN
:NEW.created_by := USER;
:NEW.created_date := SYSDATE;
ELSIF DELETING
THEN
audit_deletion(USER,SYSDATE);
39
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
END;
More on UPDATING

UPDATING may be called for partic. columns
CREATE OR REPLACE TRIGGER validate_update
BEFORE UPDATE ON account_transaction
FOR EACH ROW
BEGIN
IF UPDATING ('ACCOUNT_NO')
THEN
errpkg.raise('Account number cannot be updated');
END IF;
END;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
40
Extended auditing example



Tables: grades, grades_audit
Run: grades_tables.sql, grades_audit.sql
Cases: hacker changes grades, deletes
others
UPDATE grades
SET grade = 'A+'
WHERE student_id = 1
AND class_id = 101;
DELETE grades
WHERE student_id = 2
AND class_id = 101;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
41
Extended auditing example


Run: grades_tables.sql, grades_audit2.sql
Cases: hacker changes student or class ids
UPDATE grades SET student_id = 3
WHERE student_id = 1 AND class_id = 101;
UPDATE grades SET student_id = 1
WHERE student_id = 2 AND class_id = 101;
UPDATE grades SET student_id = 2
WHERE student_id = 3 AND class_id = 101;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
42
DDL Triggers

Respond to DDL events



Creating/dropping tables, indices, etc.
ALTER TABLE etc.
General form:
CREATE [OR REPLACE] TRIGGER trigger name
{BEFORE | AFTER| {DDL event} ON
{DATABASE | SCHEMA}
DECLARE
Variable declarations
BEGIN
... some code...
END;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
43
DDL trigger e.g.

Town crier examples triggered by creates:

uninformed_town_crier.sql

informed_town_crier.sql
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
44
Skip to: the bulk loader
Available DDL events


CREATE, ALTER, DROP, GRANT, RENAME,
REVOKE, TRUNCATE
DDL: any DDL event
CREATE OR REPLACE TRIGGER no_create
AFTER CREATE ON SCHEMA
BEGIN
RAISE_APPLICATION_ERROR (-20000,
'ERROR : Objects cannot be created in the
production database.');
END;

Q: Does this work??
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
45
DB Event triggers

Form similar to DDL triggers:
CREATE [OR REPLACE] TRIGGER trigger name
{BEFORE | AFTER} {database event} ON
{DATABASE | SCHEMA}
DECLARE
Variable declarations
BEGIN
... some code...
END;

Triggering events: STARTUP, SHUTDOWN,
SERVERERROR, LOGON, LOGOFF
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
46
DB event restrictions

Have BEFORE and AFTER as above, but they
don’t always apply:

No BEFORE STARTUP/LOGON/SERVERERROR

No AFTER SHUTDOWN/LOGOFF
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
47
DB Trigger e.g.

Gather stat before shutdown:
CREATE OR REPLACE TRIGGER on_shutdown
BEFORE SHUTDOWN ON DATABASE
BEGIN
gather_system_stats;
END;

Log error messages: error_log.sql
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
48
Trigger maintenance

Enabling & disabling:



Deleting:


DROP TRIGGER emp_after_insert;
Viewing:



ALTER TRIGGER emp_after_insert DISABLE;
ALTER TRIGGER emp_after_insert ENABLE;
select trigger_name from user_triggers;
select text from user_source where name='TOWN_CRIER';
Check validity:

select object_name, status from user_objects where
object_type='TRIGGER';
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
49
Triggers – important points





Can replace old row (result of event) with new row
Action may be performed before or after event
Can refer to old row and new row
WHEN clauses tests whether to continue
Action may be performed either




For each row involved in event
Once per event
Oracle does triggers as PL/SQL programs
A trigger runs in the same transaction as the event
triggering it
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
50
Elements of Triggers





Timing of action execution: before, after or instead
of triggering event
The action can refer to both the old and new state of
the database
Update events may specify a particular column or
set of columns
A condition is specified with an optional WHEN
clause
The action can be performed either for


once for every tuple or
once for all the tuples that are changed by the database
operation
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
51
Simple trigger example

R(id, data, last-modified)




Goal: whenever data is modified, update lastmodified date
Could modify all scripts/programs that touch this
table
CREATE TRIGGER UpdateDateTrigger


data is a large string
Last-modified is a newly added date field
Bad idea
Better: user a trigger
BEFORE UPDATE OF data ON R
REFERENCING
NEW ROW AS NewTuple
FOR EACH STATEMENT
BEGIN
NewTuple.last-modified = sysdate;
END;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
52
Triggers: Row-level example


MovieExec(name, address, cert#, netWorth)
“If someone decreases a movie executive’s net worth, I
want the database to reset itself to the previous net
worth.”
CREATE TRIGGER NetWorthTrigger
AFTER UPDATE OF netWorth ON MovieExec
REFERENCING
NEW ROW AS NewTuple
OLD ROW AS OldTuple
FOR EACH ROW
WHEN (OldTuple.netWorth>NewTuple.netWorth)
UPDATE MovieExec
SET netWorth = oldTuple.netWorth
WHERE cert# = newTuple.cert#)
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
53
Triggers: Table-level example


MovieExec(name, address, cert#, netWorth)
“If someone updates the net worth of one movie exec so that the
average net worth of all movie execs becomes less than $50,000, I
want the database to reset itself.”
CREATE TRIGGER AvgNetWorthTrigger
AFTER UPDATE OF netWorth ON MovieExec
REFERENCING
OLD TABLE AS OldStuff,
NEW TABLE AS NewStuff
FOR EACH STATEMENT
WHEN (50000 > (SELECT AVG(netWorth) FROM MovieExec))
BEGIN
DELETE FROM MovieExec
WHERE (Name, address, cert#, netWorth) IN NewStuff;
INSERT INTO MovieExec
(SELECT * FROM OldStuff);
END;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
54
Mutating Table Errors

It’s generally impossible to a row-level trigger to
modify or query the table that triggered it


 trigger 2 slides back is not allowed!
Does not apply to statement-level triggers

 trigger 1 slide back is

Can do the equiv by creating a complicated
statement-level trigger

Won’t discuss…
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
55
New topic: the bulk loader


To insert data, can insert rows one at a time
with INSERT INTO <table> VALUES(<>)
If data is in/can be computed from other
tables, can use



INSERT INTO <table> SELECT …
Often, have text file of data
MySQL’s bulk loader will parse file and insert
all into the database
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
56
Using the bulk loader

Use mysqlimport command



Takes a text file as input
Each line ~ 1 row
Tab-delimited
100
101
Max Sydow
Count Dracula
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
57
Running the bulk loader

The bulk loader is a command-line program
mysqlimport, separate from SQL*Plus:
sales% mysqlimport -hmysql2 -umyNetID -p --local my-db imptest.txt

At cmd line, specify:




user/pass (pass is optional here)
Host
http://pages.stern.nyu.edu/~mjohnson/dbms/proj4.html
Database
Input file / table name
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
58
IMPORT DATA command

Can also load data while inside mysql:
mysql> LOAD DATA LOCAL INFILE
'imptest.txt' INTO TABLE imptest;

Does not work without LOCAL

Means: reading from client (your directory), not
server
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
59
More info

If you want, you can




Use a different field separator
Reorder the fields
Import date values
For more info, see the webpages:


http://dev.mysql.com/doc/mysql/en/mysqlimport.ht
ml
http://dev.mysql.com/doc/mysql/en/load-data.html
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
60
New-old topic: Transactions

So far, have simply issued commands


Recall, though: an xact is an operation/set of
ops executed atomically


Ignored xacts
In one instant
ACID test:


Xacts are atomic
Each xact (not each statement) must leave the DB
consistent
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Default xact behavior


An xact begins upon login
By default, xact lasts until logoff
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

Except for DDL statements
They automatically commit
Examples with two views of emp…
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
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Direct xact instructions

At any point, may explicitly COMMIT:




Conversely, can ROLLBACK
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
SQL> COMMIT;
Saves all statements entered up to now
Begins new xact
SQL> ROLLBACK;
Cancels all statements entered since start of xact
Example: delete from emp; or delete junk;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
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Direct xact instructions

Remember, DDL statements are autocommitted
 They cannot be rollbacked

Examples:

drop table junk;
rollback;
truncate table junk;
rollback;

Q: Why doesn’t rollback “work”?
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
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Savepoints

Xacts are atomic
Can rollback to beginning of current xact

But might want to rollback only part way


Make 10 changes, make one bad change
Want to: roll back to before last change

Don’t have Word-like multiple undo


But do have savepoints
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
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Savepoints





Create a savepoint:
SAVEPOINT savept_name;
--changes
SAVEPOINT sp1;
emp example:
--changes
Can skip savepoints SAVEPOINT sp2;
But can ROLLBACK --changes
SAVEPOINT sp3
only backwards
--changes
Can ROLLBACK
ROLLBACK TO sp2;
only to last COMMIT ROLLBACK TO sp1;
M.P. Johnson, DBMS, Stern/NYU, Spring 2005
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AUTOCOMMIT

Finally, can turn AUTOCOMMIT on:


SQL> SET AUTOCOMMIT ON;
Then each statement is auto-committed as its
own xact

Not just DDL statements
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