DATABASE | SQL | SQL INTERVIEW QUESTION AND ANSWERS | 16 | DEFINE CONSTRAINTS? | WHAT ARE TYPES OF SUB-QUERIES? | WHAT IS SQL PROFILER? | DEFINE CLUSTERS? | DEFINE INDEXES? | WHAT IS DATA INTEGRITY?

Sql Interview Question and Answers:

91.     Define Constraints?
      Constraints is a rule or restriction concerning a piece of data that is enforced at the data level.
    A Constraint clause can constrain a single column or group of columns in a table.
    There are five types of Constraint namely
    Null / Not Null
    Primary Key
    Unique
    Check or Validation
    Foreign Key or References Key

92.     What are types of sub-queries?
      Single-row subquery, where the subquery returns only one row.
    Multiple-row subquery, where the subquery returns multiple rows.
    Multiple column subquery, where the subquery returns multiple columns.

93.     What is SQL Profiler?
      SQL Profiler is a graphical tool that allows system administrators to monitor events in an instance of Microsoft SQL Server. You can capture and save data about each event to a file or SQL Server table to analyze later.

94.     Define Clusters?

      Clustering is a method of storing tables that are intimately related and often joined together into the same area on disk.
A cluster contains one or more tables, which have one or more column in common among them.

95.     Define Indexes?
      Index is a general term for an Oracle/SQL features used to primarily to speed execution and imposes uniqueness upon certain data.
The most important of an index is to ensure uniqueness of rows and help in speedy retrieval of data.

96.     What is data integrity?
      Data integrity is an important feature in SQL Server. When used properly, it ensures that data is accurate, correct, and valid. It also acts as a trap for otherwise undetectable bugs within applications.

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