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Sunday, 10 April 2016

ICS Notes Computer Science Part 2 Chapter 6 Table and Query Short Questions

ICS Notes Computer Science Part 2 Chapter 6 Table and Query Short Questions


Q 1. What is a table?
Ans. Table is a collection of rows and columns. Each intersection of row and column is called a cell. Cell is the place where data is placed. Table is the fundamental object of relational database. Table is also known as relation. Each row represents a tuple and each column represents an attribute of an entity. Table or relation itself represents an entity.

Q 2. What is meant by degree of relation?
Ans. The number of fields of a relation is called the degree of the relation. A table's degree is specified at the time of creation. But as a rule it can be changed at any time. Change in degree of a table may cause data loss.

Q 3. What is meant by the cardinality of the relation?
Ans. The number of records in a table is called the cardinality of that table. Cardinality of a table changes as new records are added or previous records are deleted. For example a table having 40 rows/records has cardinality 40.

Q 4. What are two two table views available in Microsoft Access?
Ans. Design view and Datasheet view.

Q 5. What is Test data type?
Ans. It is the default data type of a field in MS Access. It can contain text or combination of text and numbers, as well as numbers that don't require calculations, such as  phone numbers. Its size is 255 characters or the length set by the FieldSize property, whichever is less. Microsoft Access does not reserve space for unused portions of a text field.

Q 6. What is Memo data type?
Ans. A text type field that can contain more than 64000 characters. It is used for long description.

Q 7. What is Number data type?
Ans. This field is used to store numeric data for mathematical calculations. Size of this data type can be 1. 2. 4 or 8 bytes (16 bytes if the FieldSize property is set to Replication ID).

Q 8. What is AutoNumber data type?
Ans. A unique sequential (incremented by 1) number or random number assigned by Microsoft Access whenever a new record is added to a table. AutoNumber fields can't be updated. Its size is 4 bytes.

Q 9. What is the use of Default view?
Ans. In some cases, the value of all records in a certain field is same. A default value can be set in this case. The user does not need to type the same value again and again. The property set the default value is used to set default value for a field.

Q 10. What is sorting?
Ans. Arrangement of data in a particular sequence is called sorting. The sequence can be in ascending or descending order.

Q 11. What is referential integrity?
Ans. Referential integrity is a system of rules that ensures that relationship between records in related tables are valid and that you don't accidentally delete or change related data. To enforce referential integrity both tables must have at least one common field, which have same data type and size.

Q 12. What is a query?
Ans. A query is a question that requires some data from the database. A query is created by specifying fields to display their from a table or another query. It can also specify condition for extracting data. Queries select records from one or more tables in a database.

Q 13. What is a join?
Ans. A query that extracts data from multiple tables is called join. It uses the relationship of tables to get data.

Q 14. What are wildcards?
Ans. Wildcards is a special symbol that is used in queries to search data. Some important wildcards are *, ? and #. Wildcards characters are meant to be used with fields that have the Text data type. You can sometimes use them successfully with other data types, such as dates.

Q 15. Define criteria in a query?
Ans. A condition used to limit the number of rows extracted from database is called criteria. For example, instead of viewing all the suppliers that your company uses, you can view just suppliers form China. To do this, you specify criteria that limits the results to records whose Country field is "China".

Written by: Asad Hussain

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