vu eng301 Mid Term Subjective Solved Past Paper No.1

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Standard Bar

A standard bar contains icons for functions such as file management, printing, editing, formatting and calculating. It is located just below the menu bar in an application window.

Status Bar

A horizontal line of information displayed at the bottom of an application window. It reports information about the current status of the program or the data contents in the window.

Image in HTML using the following img tag.
<IMG src=URL, alt=text height=pixels width=pixels align="bottom|middle|top">

Image in Javascript

Images in JavaScript can be manipulated in many ways using the built-in object Image. Additional properties to HTML are hspace, vspace & lowsrc.

Example: It can be used by many handlers like, onAbort, onLoad & onError

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Minimum Cardinality

This is a very important point, as minimum cardinality on one side needs special attention. Like in previous example an employee cannot exist if project is not assigned. So in that case the minimum cardinality has to be one. On the other hand if an instance of EMPLOYEE can exist with out being linked with an instance of the PROJECT then the minimum cardinality has to be zero. If the minimum cardinality is zero, then the FK is defined as normal and it can have the Null value, on the other hand if it is one then we have to declare the FK attribute(s) as Not Null. The Not Null constraint makes it a must to enter the value in the attribute(s) whereas the FK constraint will enforce the value to be a legal one. So you have to see the minimum cardinality while implementing a one to many relationship.

The intersection operation also has the requirement that both the relations should be union compatible, which means they are of same degree and same domains. It is represented by _. If R and S are two relations and we take intersection of these two relations then the resulting relation would be the set of tuples, which are in both R and S. Just like union intersection is also commutative. R _ S = S _ R (Page 154)

Normalization is basically; a process of efficiently organizing data in a database. There are two goals of the normalization process: eliminate redundant data (for example, storing the same data in more than one table) and ensure data dependencies make sense (only storing related data in a table). (Page 168)

Normal Forms

Normalization is basically; a process of efficiently organizing data in a database. There are two goals of the normalization process: eliminate redundant data (for example, storing the same data in more than one table) and ensure data dependencies make sense (only storing related data in a table). Both of these are worthy goals as they reduce the amount of space a database consumes and ensure that data is logically stored. We will now study the first normal form.There are four anomalies , redundancy ,Inset anomaliy ,delete anomaly and update anomaly.

Functional Dependencies and Keys

We can determine the keys of a relation after seeing its functional dependencies. The determinant of functional dependency that determines all attributes of that table is the super key. Super key is an attribute or a set of attributes that identifies an entity uniquely. In a table, a super key is any column or set of columns whose values can be used to distinguish one row from another. A minimal super key is the candidate key , so if a determinant of functional dependency determines all attributes of that relation then it is definitely a super key and if there is no other functional dependency whereas a subset of this determinant is a super key then it is a candidate key. So the functional dependencies help to identify keys. We have an example as under:

The relational model for database management is a database model based on first-order predicate logic The relational model provide a declarative method for specifying data and queries: we directly state what information the database contains and what information we want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for getting queries answered

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Because there is one structure and that is a relation (table). Plus this single structure is very easy to understand. Due to which a user of a moderate knowledge can understand it easily. It has strong math foundation which gives it extra strength.