Nt1330 Unit 6 Rdbms

Which of the following defines a relationship in which each occurrence of data in one entity

- Tables are useful in showing relationships and making comparisons. They should have title, row, column headings, population, source and explanations.

(TCO 7) What is the name for a unique key that is constructed from multiple columns?

3) The SQL keyword PRIMARY KEY is used to designate the column(s) that are the primary key for the table.

A(n) FOREIGN KEY constraint is used to ensure that referential integrity exists between tables. _________________________

One of the main components of a database is characters. Characters are letters, numbers and punctuation marks. You are using characters when you are typing a sentence for example. Another main component would be fields. Fields separate data in defined fields. When data is being entered even if you don’t have an answer for all fields a space is still left but it would be blank. If you have ever seen an excel spreadsheet that would give you an idea of how data is lined out into different fields. Records are a main database component as well. Records are a group of fields that are about one thing. An example would be social security numbers in a database of patients. Each patient would have a social security number and each social security number is in a field. That field would have the same information which is that patients social security number even though every ones is different and there would be many listed depending on how many patients was in the database. Gartee, R. (2011).

The example discussed above on Customers table and Orders table is a one-to-many relationship. As each customer places multiple orders, each order only belongs to one customer. When creating a relationship between two tables, if only one of the related fields is unique, a one-to-many relationship is automatically set.

An AutoNumber field or auto incremented key in a table are used to give unique values which make each record unique.

Foreign key constraints can be used to define required relationships between and with tables. When a foreign key constraint is added to an existing column or columns in the tables SQL server, by default the process will check the existing data in the column to ensure that all values, except NULL, exist in the column(s) of the referenced primary key or unique constraint.

if we have two tables, which contains a single column each, with the data as follows:

(1) Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:

Data redundancy could be defined as keeping the same piece of data in two separate places within a database or data storage technology. Traditional file-based systems stores the same information in more than one file through which space is wasted unnecessarily. But the DBMS ensure that multiple copies of the same data are not stored by integrating the files to eliminate the redundancy. Sometimes, it is necessary to duplicate key data items to model relationships. Moreover, it is desirable to duplicate some data items to improve performance. Due to above reasons DBMS does not eliminate redundancy entirely.

In SQL database, structure and data type are conform to a fixed schema. The columns must be decided and locked before data entry whereas each row must contain data in its column. To store a new data item, the entire database must be altered, during which time the database must be taken offline.

STRUCTURE OF DATA: The data structure of a relational database comprises of table structure. Every table is identified by a unique name or label. The data tables are described as the collection of rows and columns. Each row of the table is known as the record and each column is known as the field of the specific data table. All the data sets are well organized and logical linked to each other through definite and unique relationships. A table, therefore can also be defined as the “structured collection of relationships”. The fundamental aim of developing No SQL database systems is to easily and effectively handle vast quantities of data or information in advanced web-scale applications. In order to achieve this purpose, the No SQL systems are designed as the schema-free database systems. There are different modes to define the No SQL databases that typically depend on the requirements of the data that has to be managed. The data model for key-value store No SQL database is

Field-this is a column in a table that is constructed to store and maintain specific information about records that are stored in the table. They can include name, age and salary fields.