CSIS 350 โ Lecture 23
Announcments
Homework on web site โ due Thursday
Any problems creating a database?
CSIS 332 Java for the Internet
Chapter 7
Last time we started looking at SQL DDL: The CREATE TABLE statement
- define columns: name, type, constraints
- define surrogate keys
oSQL Server: IDENTITY
omySQL: AUTO_INCREMENT
- using CONSTRAINT to define FOREIGN KEYs:
oUPDATE NO ACTION, UPDATE CASCADE
oDELETE NO ACTION, DELETE CASCADE
*** You must define parent tables before child tables. This CREATE TABLE statement
will fail if the ARTIST table does not exist.
See Slides 1 & 2: Create Table statement in SQL Server and mySQL. Note the
AUTO_INCREMENT differences for defining surrogate key.
Implementing minimum cardinalities
See slide 3. Note that minimum cardinalities are enforced through the foreign key and
with the ON UPDATE and ON DELETE clauses.
Q: Why doesn't this slide show N:M relationships?
Default Value
Add DEFAULT clause to column definition. See slide 4.
Implementing data constraints
Slide 4.
Domain constraints
Range constraints
Intrarelation constraints
Note the mySQL parses these statements, but does not implement check constraints!
Also, foreign key constraints are also ignored depending upon the DB engine used.
