Mssql Interview Questions

Mssql Interview Questions Download Mssql Interview Questions PDF

Mssql Interview Questions

CDC – CDC stands for Change Data Capture, which captures the data that has been modified recently.
SQL injection – SQL injection is an attack by malicious users in which the malicious code is inserted into the strings that are passed to an instance of SQL server for parsing and execution.
All the statements have to be checked for the vulnerabilities as they execute all syntactically valid queries received.The parameters can also be changed by the experienced and skilled attackers.
Following methods are used to protect from SQL injection attack:
  • Filtering input parameters
  • Use parameter collection with Dynamic SQL
  • Use Parameters for Stored procedures
  • In like clause, use escape characters
When the index is created with WHERE clause, it is called Filter index.It is used to filter some of the rows in a table in order to improve the performance, index maintenance and reduce the index storage cost.
COMMIT – Every statement between BEGIN and COMMIT becomes persistent to the database when the COMMIT is executed.
ROLLBACK – Every statement between BEGIN and ROLLBACK are revealed to the state when the ROLLBACK is executed.
The logical operators are basically used to test the truths of conditions.
  • ALL – It returns true if all the set of operations are true.
  • AND – It returns true if the Boolean expressions are true.
  • IN – It returns true if the operand is equal to one of the lists of expressions.
  • ANY – It returns true if any of the set of comparisons is true.
  • BETWEEN – It returns true if the operand is within a range.
  • EXISTS – It returns true if the subquery contains any rows.
  • LIKE – It returns true if the operand matches a pattern
  • NOT – It reverses the values of any Boolean operator.
  • OR – It returns true if either of the Boolean expression is true.
  • SOME – It returns true if some of the set of comparisons are true.
DML (Data Manipulation Language)
  • Select
  • Insert
  • Update
  • Delete

DDL (Data Definition Language)

  • Create
  • Alter
  • Drop
  • Truncate

DCL (Data Control Language)

  • Grant
  • Revoke

TCL (Transactional Control Language)

  • Commit
  • RollBack
  • Save Transaction
UNION – It is used to select the related information.
It is similar to that of JOIN command.
UNION ALL – It is similar to that of UNION command, but it selects all the values.
It does not remove the values from the table but will retrieve the data.
TABLESAMPLE is used to extract the sample of rows that are necessary for the application.
FLOOR – It is used to round up the non-integer value to the preceding least integer.
SIGN – It is used to determine whether the number provided is positive, Zero, negative and returns +1, 0, -1.
The exceptions are handled using TRY-CATCH blocks, wherein TRY block the scripts are written and in CATCH block the errors are handled.
MSSQL stands for Microsoft Server SQL that is a Microsoft’s relational database management system. It is a featured database which is designed to compete against Oracle Database and MySQL. MSSQL is also referred as SQL Server.
SQL Server agent
The SQL Server agent plays an important part in the day to day tasks of the SQL Server Database Administrator (DBA).
Its purpose is to implement the tasks easily with the Scheduler engine that allows our tasks to run at a scheduled time and date.
Modes of Authentication in SQL Server
The two authentication modes in SQL Server are:
  • Windows Mode
  • Mixed Mode

From the tools menu of SQL Server configuration properties in the security page, the modes can be changed.

It is a tool that allows system’s administrator to monitor the events in SQL Server.It is mainly used to capture and save the data of each event of a file or a table for analysis.
COALESCE – It is a function that is used to return the first non-null expression from more than one column within the arguments.
CHECK constraint – It is used to enforce the integrity. It is applied to a column in a table to limit the values that have to be placed in a column.