The document defines lexical conventions and functional dependencies in SQL. Lexical conventions establish rules for acceptable characters in SQL statements and string literals. Functional dependencies define relationships between attributes, where a determination of one attribute value relies on the value of another attribute. There are three types of functional dependencies: full functional dependency where an attribute depends solely on another; partial functional dependency where an attribute depends on multiple other attributes; and transitive functional dependency where an attribute depends on another attribute which itself depends on a third attribute.

1. Lexical conventions defined in SQL are
1. SQL statements must consist of alphanumeric
characters , white space and the following special
characters,
 @ ! < > ‘ , ‘ ? = / $ # ( ) + - “
2. In SQL, the white space characters, tabs and
carriage returns can be interchanged and repeated.
3. Space of any type can be allowed anywhere
without any limit.
4. Comments can also be interchanged with a single
space character and can be placed anywhere.
5. String literals are enclosed in single quotes. It is
possible to put a single quote inside string literal just
by putting two quotes next to each other. Double
quotes contain equivalent of string literals inside the
string literals that has bveen passed to functions.
They must be used with column aliases containing
spaces or special characters.
FUNCTIONAL DEPENDENCIES
Functional dependency:

2. A functional dependency is defined as the
relationship between the attributes that
correspond to a single relation. In a given table, if
X and Y are two attributes of a relation and Y value
of X is used to determine the value of Y then the
attributes of a relation and the Y is used to
determine the value of Y then the attribute Y is
said to be functionally dependent on the attribute
X.Diagrammatically, a functional dependency
between X and Y attributes can be shown as,
X->Y
Example
Consider the relation EMPLOYEE in which
Emp_Id and social_security_Number are the two
attribuites. Here, if the value of
Social_Security_Number
Functional dependency is used in DBMS in the
following ways,
1. To determine whether the relations are legal.
2. To define a set of constraints on the relations.
3. To normalize the relations so as to convert the
relations into standard form.
1. Full Functional Dependency

3. If x and y are attributes of an entity set in a table
such that y is functionally dependent only on x,
but not on any proper subset of x, then this type
of dependency is called full functional
dependency.
i.e., Roll Number, Subject Name -> Marks
2. Partial Functional Dependency
If x and y are attributes of an entity set in a table
and y is functionally dependent on x such that
elimination of some attributes from x does not
effect the dependency, then this type of
dependency is called partial functional
dependency. That is, y is partially dependent on x.
Example
During examinations, any subject can be
randomly held in any examination hall. Therefore,
hall number depends on subject name as well as
roll numbers. In this case, hall number’s
dependency on subject is partial because it also
depends on roll number as well.
SubjectName-> HallNumber

4. 3.Transistent or Transitive Functional
Dependency
If x,y,z are attributes of an entity set in a table
such that x is functionally dependent on y and y
is functionally dependent on z, then z will be
transitively dependent on x through y.
Example
For examinations to be held, if students are
dependent on teachers and teachers are
dependent on management. Then management
will be transitively dependent on students
through teachers.
Students-> Teachers
Teachers->Management
Management->Students.