We have a table with a CHARACTER data type field. We apply a “>” row comparison between this field and another CHARACTER field in another table. What will be the results for records with field value of NULL

This is something  so many asked me because I also faced the same situation before, so having a NULL in a row when compared will give an UNKNOWN result.

The result will not be correct hence creates an ambiguity.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com)

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SQL SERVER – CREATE INDEX myIndex ON myTable(myColumn)What type of Index will get created after executing the above statement

Non-clustered index. Important thing to note: By default a clustered index gets created on the primary key, unless specified otherwise.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )

SQL SERVER – what are the DBCC commands that are commonly use for database maintenance

DBCC CHECKDB, DBCC CHECKTABLE, DBCC CHECKCATALOG, DBCC CHECKALLOC, DBCC SHOWCONTIG, DBCC SHRINKDATABASE, DBCC SHRINKFILE etc. But there are a whole load of DBCC commands which are very useful for DBAs. Check out SQL Server books online for more information.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )

SQL SERVER 2008 – How to rename a column

There are many ways where in we can  rename  a column but what I prefer is using predefined stored Procedure sp_rename .

Syntax :

exec sp_rename ‘tablename.ColumnName’, ‘NewColumnName’, ‘column’ –objecttype

EX: changing the column name “Name” to “FirstName”

create table Personal(ID int, Name varchar(50))

EXEC sp_rename ‘Personal.Name’, ‘FirstName’, ‘column’

Output:

The message displayed is a caution message that says when we alter the column name there is a possibility that it can be used in one or more stored procedures so make sure you update everything and then only change the name .

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )

SQL SERVER – What is the difference between group by and order by

Group by controls the presentation of the rows, order by controls the presentation of the columns  for the results of the SELECT statement.

EX 1 : Group By helps us display any aggregate of any column based on a field what has repeated names.

use AdventureWorksDW2008R2

go

select Title,SUM(BaseRate) as Rate  from dbo.DimEmployee group by Title

Output:

EX 2 : Order By clause helps us display any table based on the values present on that particular column.

use AdventureWorksDW2008R2

go

select FirstName,Title  from dbo.DimEmployee order by FirstName

the difference is how we choose and what is the reuirement.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )

SQL SEREVER – What is a View and An Indexed View

 A view  is a virtual tables that is made up of one or more tables. It can be used for security purpose, hiding complex queries.

An Indexed view is a view that has unique clustered index created on it. This takes physical storage i.e it stores data. It will be used in OLAP, decision support where inserts/updates are low. It can be used in the following scenarios

1) Joins and aggregation of big tables.

2) Repeated joins of the same tables on the same keys.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )

SQL SERVER 2008 – What is the difference betweeen Execute and sp_executesql

sp_executesql and Execute statement are used to execute a sql stored Procedure. The execute statement doesn’t support parameter substitution in the executed string.

According to Sql server Book Online Link Here.

‘To execute a string, we recommend that you use the sp_executesql stored procedure instead of the EXECUTE statement. Because this stored procedure supports parameter substitution, sp_executesql is more versatile than EXECUTE; and because sp_executesql generates execution plans that are more likely to be reused by SQL Server, sp_executesqlis more efficient than EXECUTE.’

So the best thing to use is sp_executesql but depends according to the requirement.

Reference : Dilip Kumar Jena ( https://sqlexplore.wordpress.com )