Oracle Certification Questions

Maximim number of triggers that can be applied to a single table is 12

Integrity constraints are used to ensure accuracy and consistency of data in a relational database. Data integrity is handled in a relational database through the concept of referential integrity. Many types of integrity constraints play a role in referential integrity (RI).

Hence, Data integrity constraints are used to Improve the quality of data entered for a specific property i.e, table column.

Count function in SQL returns the number of values or rows.

LIKE, BETWEEN and = operators are used for comparison in SQL. Comparison operators test whether two expressions are the same. Comparison operators can be used on all expressions except expressions of the text, ntext, or image data types.

The collections of entities of a particular Entity Type are grouped together into an entity set.

Breaking of relationships is prevented once referential integrity on a database is enforced

Because a table can have only one primary key

Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as Primary Key. 

Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.

• One needs to be very careful in selecting the Primary Key as an incorrect selection can adversely impact the database architect and future normalization. For a Candidate Key to qualify as a Primary Key, it should be Non-NULL and unique in any domain.