1. Perbedaan Union Dan Union All Access
2. Apa Perbedaan Union Dan Union All
3. Perbedaan Union Dan Union Alliance

By: Last Updated: 2007-12-05 Related Tips: ProblemSometimes there is a need to combine data from multiple tables or views into one comprehensive dataset. This may be for tableswith similar data within the same database or maybe there is a need to combinesimilar data across databases or even across servers. In this tip we will takea look at the how to use UNIONvs. UNION ALL commands and how they differ. SolutionIn SQL Server you have the ability to combine multiple datasets into one comprehensive dataset by using the UNIONvs. UNION ALL operators.

There is a big difference in how these work as well as the final result set that is returned, but basically these commands join multiple datasets that have similar structures into one combined dataset.Here is a brief description:. UNION - this operation will allow you to join multiple datasets into one dataset and will remove any duplicates that exist. Basically it is performing a DISTINCT operation across all columns in the result set. UNION ALL - this operation again allows you to join multiple datasets into one dataset, but it does not remove any duplicate rows. Because this does not remove duplicate rows this process is faster, but if you don't want duplicate records you will need to use the UNION operator instead.Rules to union data:.

Each query must have the same number of columns. Each column must have compatible data types. Column names for the final result set are taken from the first query. ORDER BY and COMPUTE clauses can only be issued for the overall result set and not within each individual result set. GROUP BY and HAVING clauses can only be issued for each individual result set and not for the overall result set.

TipIf you don't have the exact same columns in all queries use a default value or a NULL value such as:SELECT firstName, lastName, company FROM businessContactsUNIONSELECT firstName, lastName, NULL FROM nonBusinessContactsorSELECT firstName, lastName, createDate FROM businessContactsUNION ALLSELECT firstName, lastName, getdate FROM nonBusinessContactsUNION vs. UNION ALL ExamplesLet's take a look at a few simple examples of how these commands work and how they differ. As you will see the final resultsets will differ, but there is some interesting info on how SQL Server actually completes the process. UNION ALLIn this first example we are using the UNION ALL operator against the Employee table from the AdventureWorks database.

This is probably not something you would do, but this helps illustrate the differences of these two operators.There are 290 rows in table dbo.Employee. SELECT. FROM HumanResources.EmployeeUNIONSELECT. FROM HumanResources.EmployeeUNIONSELECT. FROM HumanResources.EmployeeWhen this query is run the result set has 290 rows.

Perbedaan Union Dan Union All Access

Even though we combined the data three times the UNION operator removed the duplicate records and therefore returns just the 290 unique rows.Here is the execution plan for this query. We can see that SQL Server first queried 2 of the tables, then did a Merge Join operation to combine the first two tables and then it did another Merge Join along with querying the third table in the query. So we can see there was much more worked that had to be performed to get this result set compared to the UNION ALL. Post a comment or let the author know this tip helped.All comments are reviewed, so stay on subject or we may delete your comment.

Note: your email address is not published. Required fields are marked with an asterisk (.).Name.EmailEmail me updates. NOTE. If you want to include code from SQL Server Management Studio (SSMS) in your post, please copy the code from SSMS and paste the code into a text editor like NotePad before copying the code below to remove the SSMS formatting.Signup for our newsletterI agree by submitting my data to receive communications, account updates and/or special offers about SQL Server from MSSQLTips and/or its Sponsors. I have read the and understand I may unsubscribe at any time.

Apa Perbedaan Union Dan Union All

The a/an-rule is based on pronunciation, not on spelling. Though the word union is spelt beginning with a vowel, the u is pronounced 'you':/ˈjuː.ni.ən/So, this is why it is accompanied by a rather than an and this is also the case for many other words starting with a vowel, have a look at these:. a user. a Europeanbut:. an ultimatum. an orangeNote that there are words which start with an h and when that h is not pronounced, these words also go with an:an honorHowever, if this h is pronounced, then the article used is a:.

Perbedaan Union Dan Union Alliance

a hill. a heathenHere's a short but clear article that explains the usage of a/an.