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Home >> Interview Question >> Sql Server >> Post New Question Subscribe to Interview Questions

which is Faster Union or Union All?

Posted By :Narayanan     Posted Date :April 12, 2013    Points :40   Category :Sql Server 
Union All is faster than union in SQL Server

You can also find related Interview Question to which is Faster Union or Union All?  below: 

What is the difference between UNION ALL Statement and UNION

  
The main difference between UNION ALL statement and UNION is UNION All statement is much faster than UNION.
Reason : Because UNION ALL statement does not look for duplicate rows, but on the other hand UNION statement does look for duplicate rows, whether or not they exist. (More...)

Difference between UNION and UNION in SQL ?

  
UNION : Doesn't return Duplicate Values.
UNION ALL: return All values (includes Duplicate Values) (More...)

Difference between:UNION and INTERSET?

  
UNION: OR operator (value is selected if it appears in either the first or the second statement)
INTERSET:AND operator (value is selected only if it appears in both statements). (More...)

What is difference between Union and Union All

  
Union will filter duplicate values where as union all will not filter duplicate values (More...)

What is the difference among UNION, MINUS and INTERSECT

  
UNION combines the results from 2 tables and eliminates duplicate records from the result set.

MINUS operator when used between 2 tables, gives us all the rows from the first table except the rows which are present in the second table.

INTERSECT operator returns us only the matching or common rows between 2 result sets. (More...)

What is the difference between UNION and UNION ALL

  
UNION and UNION ALL both unify for add two structurally similar data sets, but UNION operation returns only the unique records from the resulting data set whereas UNION ALL will return all the rows, even if one or more rows are duplicated to each other. (More...)

What is the difference between JOIN and UNION

  
SQL JOIN allows us to "lookup" records on other table based on the given conditions between two tables. For example, if we have the department ID of each employee, then we can use this department ID of the employee table to join with the department ID of department table to lookup department names. (More...)

List or HashSet seems to be faster?

  
HashSet is than faster list? (More...)

Which one is faster?
int.Parse()
int.TryParse()
Convert.ToInt32()

  
int.TryParse() is relativly faster when compared to others (More...)

Is a java script script faster than an ASP script?

  
Since javas cript is a client-side script it does require the web server's help for its computation,so it is always faster than any server-side script like ASP,PHP,JSP etc. (More...)

Which is faster a WebPart or a User Control?

  
Ans. A WebPart renders faster than a User Control. A User Control in SharePoint is usually loaded by a webpart which adds an overhead. User Controls however, gives you an Interface to add controls and styles. (More...)

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