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What is difference between DELETE and TRUNCATE commands?

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 en…

What's the difference between a primary key and a unique key?

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.

What are different types of Collation Sensitivity?

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.

What are the different index configurations a table can have?

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

Schema Binding and Indexed Views in SQL Server

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 without sc…

Which of the following ranking functions distribute the rows in an ordered partition into a specified number of groups

Which of the following ranking functions distribute the rows in an ordered partition into a specified number of groups?A. ROW_NUMBERB. RANKC. DENSE_RANKD. NTILEE. 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 consecutive integers.

The…

@@IDENTITY VS SCOPE_IDENTITY() VS IDENT_CURRENT

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 than any iden…