Sql Code Masterz

Both primary key and unique key enforces uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs , but unique key allows one NULL only .

Case sensitivity - A and a, B and b, etc.   Accent sensitivity   Kana Sensitivity - When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.   Width sensitivity - A single-byte character (half-width) and the same character represented as a double-byte character (full-width) are treated differently than it is width sensitive.

A table can have one of the following index configurations: No indexes  A clustered index A clustered index and many nonclustered indexes A nonclustered index Many nonclustered indexes

Problem Recently while creating an archival job I noticed that job was taking way too long to complete. To help troubleshoot I executed the stored procedure directly and it was also taking a long time to fetch the rows from the view that I was using. Based on the query plan it looked like creating an index on the view may help the issue, so I first looked to see if any indexes were in place for the views, but none were found. The next step was to create an index on the view, but I was presented with this error message "Cannot create index on view, because the view is not schema bound". Solution The error message "Cannot create index on view '*' because the view is not schema bound. (Microsoft SQL Server, Error: 1939)" clearly suggested that in order to create an index on this view I have to make it schema bound, but what is schema binding and how does this work? Schema binding ties an object to the base object that this new object depends upon. So ...

Which of the following ranking functions distribute the rows in an ordered partition into a specified number of groups? A. ROW_NUMBER B. RANK C. DENSE_RANK D. NTILE E. None of the Above Ans :- D Explanation:- The NTILE ranking function distributes the rows in an ordered partition into a specified number of groups. The groups are numbered, starting at one. For each row, NTILE returns the number of the group to which the row belongs. The ROW_NUMBER ranking function returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition. The RANK ranking function returns the rank of each row within the partition of a result set. The rank of a row is one plus the number of ranks that come before the row in question. Just like the DENSE_RANK, in the RANK ranking function, if two or more rows tie for a rank, each tied rows receive the same rank. Unlike the DENSE_RANK, the RANK ranking function does not always return con...

SELECT @@IDENTITY It returns the last IDENTITY value produced on a connection, regardless of the table that produced the value, and regardless of the scope of the statement that produced the value. @@IDENTITY will return the last identity value entered into a table in your current session. While @@IDENTITY is limited to the current session, it is not limited to the current scope. If you have a trigger on a table that causes an identity to be created in another table, you will get the identity that was created last, even if it was the trigger that created it. SELECT SCOPE_IDENTITY() It returns the last IDENTITY value produced on a connection and by a statement in the same scope, regardless of the table that produced the value. SCOPE_IDENTITY(), like @@IDENTITY, will return the last identity value created in the current session, but it will also limit it to your current scope as well. In other words, it will return the last identity value that you explicitly created, rather t...

What are the SQL Server system databases and can you outline the general functionality of each database? Master - Database responsible for SQL Server instance related data.  You can also think of this database corresponding to the Windows SQL Server service account. Resource - Database responsible for SQL Server system objects.  This database was introduced in SQL Server 2005 and is intended to ease the upgrade and rollback of SQL Server system objects. Model - Template database for the creation of new user defined databases. MSDB - Database responsible for SQL Server Agent related data such as Jobs, Alerts, Operators, etc. TempDB - Temporary database to store temporary tables (#temptable or ##temptale), table variables, cursors, work tables, row versioning, create or rebuild indexes sorted in TempDB, etc.  Each time the SQL Server instance is restarted all objects in this database are destroyed, so permanent objects cannot be created in this databa...

ACID (an acronymn for Atomicity Consistency Isolation Durability) is a concept that Database Professionals generally look for when evaluating databases and application architectures. For a reliable database all this four attributes should be achieved. Atomicity is an all-or-none proposition. Consistency guarantees that a transaction never leaves your database in a half-finished state. Isolation keeps transactions separated from each other until they’re finished. Durability guarantees that the database will keep track of pending changes in such a way that the server can recover from an abnormal termination. Above four rules are very important for any developers dealing with databases. Reference : Pinal Dave ( http://blog.SQLAuthority.com )

What is XML Datatype? The xml data type lets you store XML documents and fragments in a SQL Server database. An XML fragment is an XML instance that is missing a single top-level element. You can create columns and variables of the xml type and store XML instances in them. The xml data type and associated methods help integrate XML into the relational framework of SQL Server.

Which are new data types introduced in SQL SERVER 2008? The GEOMETRY Type: The GEOMETRY data type is a system .NET common language runtime (CLR) data type in SQL Server. This type represents data in a two-dimensional Euclidean coordinate system. The GEOGRAPHY Type: The GEOGRAPHY datatype’s functions are the same as with GEOMETRY. The difference between the two is that when you specify GEOGRAPHY, you are usually specifying points in terms of latitude and longitude. New Date and Time Datatypes: SQL Server 2008 introduces four new datatypes related to date and time: DATE, TIME, DATETIMEOFFSET, and DATETIME2. DATE : The new DATE type just stores the date itself. It is based on the Gregorian calendar and handles years from 1 to 9999. TIME : The new TIME ( n ) type stores time with a range of 00:00:00.0000000 through 23:59:59.9999999. The precision is allowed with this type. TIME supports seconds down to 100 nanoseconds. The n in TIME ( n ) defines this level of f...

What is MERGE Statement? MERGE is a new feature that provides an efficient way to perform multiple DML operations. In previous versions of SQL Server, we had to write separate statements to INSERT, UPDATE, or DELETE data based on certain conditions, but now, using MERGE statement we can include the logic of such data modifications in one statement that even checks when the data is matched then just update it and when unmatched then insert it. One of the most important advantages of MERGE statement is all the data is read and processed only once.

What is CTE? CTE is an abbreviation Common Table Expression. A Common Table Expression (CTE) is an expression that can be thought of as a temporary result set which is defined within the execution of a single SQL statement . A CTE is similar to a derived table in that it is not stored as an object and lasts only for the duration of the query

What is Replication and Database Mirroring? Database mirroring can be used with replication to provide availability for the publication database. Database mirroring involves two copies of a single database that typically reside on different computers. At any given time, only one copy of the database is currently available to clients which are known as the principal database. Updates made by clients to the principal database are applied on the other copy of the database, known as the mirror database. Mirroring involves applying the transaction log from every insertion, update, or deletion made on the principal database onto the mirror database.

What is Service Broker? Service Broker is a message-queuing technology in SQL Server that allows developers to integrate SQL Server fully into distributed applications. Service Broker is feature which provides facility to SQL Server to send an asynchronous, transactional message. it allows a database to send a message to another database without waiting for the response, so the application will continue to function if the remote database is temporarily unavailable

What is an execution plan? When would you use it? How would you view the execution plan? An execution plan is basically a road map that graphically or textually shows the data retrieval methods chosen by the SQL Server query optimizer for a stored procedure or ad-hoc query and is a very useful tool for a developer to understand the performance characteristics of a query or stored procedure since the plan is the one that SQL Server will place in its cache and use to execute the stored procedure or query. From within Query Analyzer is an option called “Show Execution Plan” (located on the Query drop-down menu). If this option is turned on it will display query execution plan in separate window when query is ran again.

What is DataWarehousing? Subject-oriented, meaning that the data in the database is organized so that all the data elements relating to the same real-world event or object are linked together; Time-variant, meaning that the changes to the data in the database are tracked and recorded so that reports can be produced showing changes over time; Non-volatile, meaning that data in the database is never over-written or deleted, once committed, the data is static, read-only, but retained for future reporting. Integrated, meaning that the database contains data from most or all of an organization’s operational applications, and that this data is made consistent.

What is Identity? Identity (or AutoNumber) is a column that automatically generates numeric values. A start and increment value can be set, but most DBA leave these at 1. A GUID column also generates numbers; the value of this cannot be controlled. Identity/GUID columns do not need to be indexed.

What are different Types of Join? Cross Join A cross join that does not have a WHERE clause produces the Cartesian product of the tables involved in the join. The size of a Cartesian product result set is the number of rows in the first table multiplied by the number of rows in the second table. The common example is when company wants to combine each product with a pricing table to analyze each product at each price. Inner Join A join that displays only the rows that have a match in both joined tables is known as inner Join.  This is the default type of join in the Query and View Designer. Outer Join A join that includes rows even if they do not have related rows in the joined table is an Outer Join.  You can create three different outer join to specify the unmatched rows to be included: Left Outer Join: In Left Outer Join all rows in the first-named table i.e. “left” table, which appears leftmost in the JOIN clause are included. Unmatched rows i...

Can a stored procedure call itself or recursive stored procedure? How many level SP nesting possible? Yes. Because Transact-SQL supports recursion, you can write stored procedures that call themselves. Recursion can be defined as a method of problem solving wherein the solution is arrived at by repetitively applying it to subsets of the problem. A common application of recursive logic is to perform numeric computations that lend themselves to repetitive evaluation by the same processing steps. Stored procedures are nested when one stored procedure calls another or executes managed code by referencing a CLR routine, type, or aggregate. You can nest stored procedures and managed code references up to 32 levels.

What is SQL server agent? SQL Server agent plays an important role in the day-to-day tasks of a database administrator (DBA). It is often overlooked as one of the main tools for SQL Server management. Its purpose is to ease the implementation of tasks for the DBA, with its full-function scheduling engine, which allows you to schedule your own jobs and scripts.