Question 1

What are PL/SQL cursor exceptions?

Accepted Answer

Cursor_Already_Open, Invalid_Cursor

Question 2

How can you find a PL/SQL block, if the cursor is open?

Accepted Answer

By use of %ISOPEN status variable

Question 3

How can you generate debugging output from PL/SQL?

Accepted Answer

Use the DBMS_OUTPUT package Another possible method is to use the SHOW ERROR command

Question 4

State one similarity and difference between WHERE Clause and HAVING Clause?

Accepted Answer

Similarity: Both WHERE and HAVING Clause filters out records based on one or more conditions Difference: WHERE Clause can only be applied to a static non-aggregated column whereas HAVING is needed for aggregated columns

Question 5

What are defaults? Is there a column to which a default can’t be bound?

Accepted Answer

A default is a value which will be used by a column, if no value is supplied to that column while inserting data Yes, IDENTITY and TIMESTAMP columns are free from the bounds of default

Question 6

What are constraints? Mention the different types of constraints?

Accepted Answer

Constraints enable the RDBMS to enforce the integrity of the database automatically, without the need to create triggers, rule or defaults Types of Constraints: NOT NULL, CHEQUE, UNIQUE, PRIMARY KEY, FOREIGN KEY

Question 7

What is the difference between a primary key and a unique key?

Accepted Answer

By default, primary key creates a clustered index on the column, whereas a unique key creates a non clustered index by default

Question 8

What are the difference between clustered and a non-clustered index?

Accepted Answer

- A clustered index is a special type of index that reorders the way records in the table are physically stored Therefore table can have only one clustered index The leaf nodes of a clustered index contain the data pages - A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk The leaf node of a non clustered index does not consist of the data pages Instead, the leaf nodes contain index rows

Question 9

What is difference between DELETE and TRUNCATE commands?

Accepted Answer

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command TRUNCATE: - TRUNCATE is faster and uses fewer system and transaction log resources than DELETE - TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log - TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains The counter used by an identity for new rows is reset to the seed for the column - You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint Because TRUNCATE TABLE is not logged, it cannot activate a trigger - TRUNCATE cannot be rolled back - TRUNCATE is DDL Command - TRUNCATE Resets identity of the table DELETE: - DELETE removes rows one at a time and records an entry in the transaction log for each deleted row - If you want to retain the identity counter, use DELETE instead If you want to remove table definition and its data, use the DROP TABLE statement - DELETE Can be used with or without a WHERE clause - DELETE Activates Triggers - DELETE can be rolled back - DELETE is DML Command - DELETE does not reset identity of the table Note: DELETE and TRUNCATE both can be rolled back when surrounded by TRANSACTION if the current session is not closed If TRUNCATE is written in Query Editor surrounded by TRANSACTION and if session is closed, it can not be rolled back but DELETE can be rolled back

Question 10

Can SQL Servers linked to other servers like Oracle?

Accepted Answer

SQL Server can be linked to any server provided it has OLE-DB provider from Microsoft to allow a link Eg Oracle has an OLE-DB provider for oracle that Microsoft provides to add it as linked server to SQL Server group

Question 11

What is Log Shipping?

Accepted Answer

Log shipping is the process of automating the backup of database and transaction log files on a production SQL server, and then restoring them onto a standby server Enterprise Editions only supports log shipping In log shipping the transactional log file from one server is automatically updated into the backup database on the other server If one server fails, the other server will have the same db and can be used this as the Disaster Recovery plan The key feature of log shipping is that it will automatically backup transaction logs throughout the day and automatically restore them on the standby server at defined interval

Question 12

Where SQL server user names and passwords are stored in SQL server?

Accepted Answer

They get stored in System Catalog Views sysserver_principals and syssql_logins

Question 13

What is LINQ?

Accepted Answer

Language Integrated Query (LINQ) adds the ability to query objects using NET languages The LINQ to SQL object/relational mapping (O/RM) framework provides the following basic features: - Tools to create classes (usually called entities) mapped to database tables - Compatibility with LINQ's standard query operations - The DataContext class, with features such as entity record monitoring, automatic SQL statement generation, record concurrency detection, and much more

Question 14

What is Aggregate Functions?

Accepted Answer

Aggregate functions perform a calculation on a set of values and return a single value Aggregate functions ignore NULL values except COUNT function HAVING clause is used, along with GROUP BY, for filtering query using aggregate values Following functions are aggregate functions AVG, MIN CHECKSUM_AGG, SUM, COUNT, STDEV, COUNT_BIG, STDEVP, GROUPING, VAR, MAX VARP

Question 15

How to rebuild Master Database?

Accepted Answer

Master database is system database and it contains information about running server's configuration When SQL Server 2005 is installed it usually creates master, model, msdb, tempdb resource and distribution system database by default Only Master database is th one which is absolutely must have database Without Master database SQL Server cannot be started This is the reason it is extremely important to backup Master database To rebuild the Master database, Run Setupexe, verify, and repair a SQL Server instance, and rebuild the system databases This procedure is most often used to rebuild the master database for a corrupted installation of SQL Server

Question 16

What UNION does in SQL?

Accepted Answer

In SQL, UNION merges the contents of two structurally-compatible tables into a single combined table

Question 17

The multi part identifier could not be bound is

Accepted Answer

One of the most common errors that you might face in join statements is Server: Msg 4104, Level 16, State 1, Line 1 The multi-part identifier could not be bound A multipart identifier is any description of a field or table that contains multiple parts - for instance MyTableSomeRow - if it can't be bound that means there's something wrong with it - either you've got a simple typo, or a confusion between table and column It can also be caused by using reserved words in your table or field names and not surrounding them with [] The main reason for this error is that the source table cannot be found, for example if you have statement such as Table1OrderDate, and then if you get error above, this means that Table1 cannot be found in the query Sometimes you can see that source table exists in the query, but T-SQL cannot understand it, especially when you write join statements

Question 18

What operator tests column for the absence of data?

Accepted Answer

SELECT "column_name" FROM "table_name" WHERE "column_name" IS NULL.

Question 19

Which one of the following sorts rows in SQL?

Accepted Answer

ORDER BY

Question 20

Which of the following statements is true concerning subqueries?

Accepted Answer

Involves the use of an inner and outer query.

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