SQL SERVER – Tips from the SQL Joes 2 Pros Development Series – Aggregates with the Over Clause – Day 10 of 35

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Aggregates with the Over Clause

You have likely heard the business term “Market Share”. If your company is the biggest and has sold 15 million units in an industry that has sold a total of 50 million units then your company’s market share is 30% (15/50 = .30). Market share represents your number divide by the sum of all other numbers. In JProCo the biggest grant (Ben@Moretechnology.com) is $41,000 and the total of all grants is $193,700. Therefore the Ben grant is 21.6% of the whole set of grants for the company.

The two simple queries in the figure below show all the Grant table records and the sum of the grant amounts.

SQL SERVER - Tips from the SQL Joes 2 Pros Development Series - Aggregates with the Over Clause - Day 10 of 35 j2p_10_1

If we want to show the total amount next to every record of the table – or just one record of the table – SQL Server gives us the same error. It does not find the supporting aggregated language needed to support the SUM( ) aggregate function.

SQL SERVER - Tips from the SQL Joes 2 Pros Development Series - Aggregates with the Over Clause - Day 10 of 35 j2p_10_2

Solarwinds

Adding the OVER( ) clause allows us to see the total amount next to each grant. We see 193,700 next to each record in the result set.

SQL SERVER - Tips from the SQL Joes 2 Pros Development Series - Aggregates with the Over Clause - Day 10 of 35 j2p_10_3

The sum of all 10 grants is $193,700. Recall the largest single grant (007) is $41,000. Doing the quick math in our head, we recognize $41,000 is around 1/5 of ~$200,000 and guesstimate that Grant 007 is just over 20% of the total.

SQL SERVER - Tips from the SQL Joes 2 Pros Development Series - Aggregates with the Over Clause - Day 10 of 35 j2p_10_4

Thanks to the OVER clause, there’s no need to guess. We can get the precise percentage. To accomplish this, we will add an expression that does the same math we did in our head. We want the new column to divide each grant amount by $193,700 (the total of all the grants).

By listing the total amount of all grants next to each individual grant, we automatically get a nice reference for how each individual grant compares to the total of all JProCo grants. The new column is added and confirms our prediction that Grant 007 represents just over 21% of all grants.

SQL SERVER - Tips from the SQL Joes 2 Pros Development Series - Aggregates with the Over Clause - Day 10 of 35 j2p_10_5

Notice that the figures in our new column appear as ratios. Percentages are 100 times the size of a ratio. Example:  the ratio 0.2116 represents a percentage of 21.16%. Multiplying a ratio by 100 will show the percentage. To finish, give the column a descriptive title, PercentOfTotal.

In today post we examined the basic over clause with an empty set of Parenthesis. The over clause actually have many variations which we will see in tomorrow’s post.

Note: If you want to setup the sample JProCo database on your system you can watch this video. For this post you will want to run the SQLQueriesChapter5.0Setup.sql script from Volume 2.

Question 10

You want to show all fields of the Employee table. You want an additional field called StartDate that shows the first HireDate for all Employees. Which query should you use?

  1. SELECT *, Min(HireDate) as StartDate FROM Employee
  2. SELECT *, Max(HireDate) as StartDate FROM Employee
  3. SELECT *, Min(HireDate) OVER() as StartDate FROM Employee
  4. SELECT *, Max(HireDate) OVER() as StartDate FROM Employee

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124 Comments. Leave new

  • The correct option is #3

    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Option 1 and 2 would generate errors. Aggregate functions used in this context would need a GROUP BY statement.

    Option 4 grabs the Max(HireDate) which would be the last, not the first, hire date of all of the employees.

    Reply
  • A. Arul Prakash
    August 11, 2011 2:44 am

    correct answer : 3
    3) SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Minimum of Hiredate will be first hire date. And since there is no group by clause, 1) is invalid. 3) with over() clause will put the earliest hire date in each row.

    Country : USA

    Reply
  • Osvaldo Alvarez Bobadilla.
    August 11, 2011 3:27 am

    Hola, interesante proyecto que sigo hace un par de años.

    Aunque no corresponda mi participación, ya que, no vivo en India o EEUU, la respuesta correcta es la número 3.

    Determina la menor fecha de contratación y la asocia a todas las ocurrencias que existen en la tabla..

    (Option 3: SELECT *, Min(HireDate) OVER() as StartDate FROM Employee)

    Vivo en Santiago de Chile,

    Reply
  • Answer: Option #3

    If you do not use OVER() you will get an error in your query. Also, you want the FIRST hire date, so you do not want to use MAX(), which leaves only option #3.

    Country: United States

    Reply
  • Kelly (@greeleygeek)
    August 11, 2011 6:53 am

    #3 SELECT *, Min(HireDate) OVER() as StartDate FROM Employee
    Kelly
    USA

    Reply
  • Correct answer is option 3

    Reply
  • Srikanth Nallamothu
    August 11, 2011 11:48 am

    3.SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Reply
  • The correct answer is option 3

    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Cochin,INDIA

    Reply
  • Answer is 3 option
    India

    Reply
  • Prasanna kumar.D
    August 11, 2011 7:36 pm

    Answer for today question – Option : 3
    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Today blog is useful to know over clause in SQL

    Chennai, Tamilnadu, India

    Reply
  • Hello

    Love this series. The correct answer is #3, SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Thanks
    Eric
    USA

    Reply
  • The correct answer is the #3

    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Regards,
    Francisco
    Miami

    Reply
  • Q 10) SQL SERVER – Tips from the SQL Joes 2 Pros Development Series – Aggregates with the Over Clause – Day 10 of 35

    A.) Because there is no supporting language for the aggregated field both (1) and (2) will not be correct. Because Max (HireDate) will return the greatest or most recent HireDate (4) is also incorrect. The correct code is (3) which uses the Min aggregate function and the OVER ( ) clause as supporting language.

    Winner from USA: levpius

    Winner from India: Deva Rajan

    I thank you all for participating here. The permanent record of this update is posted on facebook page.

    Reply
  • correct answer is

    3.SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Country:India
    hyderabad

    Reply
  • select *,HIREDATE -max(hiredate) over() as diff from emp2

    Reply
  • Uday Bhoopalam
    August 16, 2011 9:58 pm

    Correct answer is #3. I am coming across over() for the first time

    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Uday
    USA

    Reply
  • Answer is #3:
    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    Thanks,
    Wayne (USA(

    Reply
  • Suvendu Shekhar Giri
    October 16, 2011 12:57 pm

    It helped me a lot , Thanks

    Reply
  • Krishnat Patil
    July 19, 2012 1:35 pm

    The correct answer is option 3

    SELECT *, Min(HireDate) OVER() as StartDate FROM Employee

    INDIA

    Reply

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