Slide 6.12: SQL (Structured Query Language)

Slide 6.11: Relational databases and SQL
Slide 6.13: SQL (cont.)
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SQL (Structured Query Language)

SQL Naming Conventions
A naming convention is a set of unwritten rules that you should use if you want to increase the readability of the whole data model:

All SQL commands should be written in uppercase letters.
Use lower letters when naming database objects.
Use the singular for the table or column name such as .
If the name includes more than one word, use underscore to connect them like .
It would be the best to simply name a primary key column
Foreign key columns store values from the range of primary key of the referenced table, and you should use that table name and , e.g., .
The name or variable uses the italic font style or symbol font if it is used in text.

CREATE TABLE

CREATE TABLE table-name (
  column-name-1 type [NOT NULL | UNIQUE] [, column-name-2 ... ]
  ...
  [, UNIQUE ( list-of-column-names ) [, UNIQUE ... ] ]
  [, PRIMARY KEY ( list-of-column-names ) ]
  [, FOREIGN KEY ( list-of-column-names )
      REFERENCES  table-name-2 [ ( list-of-column-names ) ]
  [, FOREIGN KEY ... ] ]
  [, CHECK ( condition ) [, CHECK ... ] ] )

Key (PRIMARY KEY) means an attribute or attribute combination whose values uniquely identify the tuples of any relation.

Foreign key (FOREIGN KEY) defined for a schema , however, describes an attribute or attribute combination which is a key in another schema (REFERENCES); the meaning of a foreign key relationship between and via attribute is that the part of is a subset of the part of .

SQL> DROP TABLE  student;
SQL> CREATE TABLE  student (
  2    student_id   CHAR(4) PRIMARY KEY,
  3    last_name    VARCHAR(32),
  4    first_name   VARCHAR(32),
  5    class        INTEGER,
  6    phone        VARCHAR(16) );

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Slide 6.11: Relational databases and SQL
Slide 6.13: SQL (cont.)
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