Case function with an alias - sql

Question

I wish to use CASE statement with an alias that resulted of a quotient of two columns.
The code that I wrote is the follow, but it returns an error.
Could anyone help me with this?
SELECT TOP 5(ROUND(Registered_Students/Total_Student * 100,2)) AS Porcentaje, C.Total_Student, C.Registered_Students, S.Subject_Name, DATEPART(Year, C.Date) AS Año,
CASE WHEN Porcentaje >= 75 THEN 'Elected'
WHEN Porcentaje >= 50 THEN 'Elected 1'
ELSE 'Not elected' AS Elections
FROM Cohort AS C
INNER JOIN Subject AS S
ON S.Id_Subject = C.Id_Subject
ORDER BY Porcentaje

Answer 1

the syntax of SQL server case statement is not correct:
SELECT column1,
column2,
CASE WHEN CONDITION THEN 'Value1'
ELSE 'Value2' END AS columnX
FROM table
you just need to add END in your syntax and it will work fine

Answer 2

you have to insert the word; 'END' end of the line
SELECT C.Total_Student, C.Registered_Students, S.Subject_Name, DATEPART(Year, C.Date) AS Año,
CASE WHEN Porcentaje >= 75 THEN 'Elected'
WHEN Porcentaje >= 50 THEN 'Elected 1'
ELSE 'Not elected' END AS Elections
FROM Cohort AS C
INNER JOIN Subject AS S
ON S.Id_Subject = C.Id_Subject
ORDER BY Porcentaje
as-is
ELSE 'Not elected' AS Elections
to-be
ELSE 'Not elected' END AS Elections

Answer 3

A column alias can't be referenced in the same SELECT clause as it is created. Have a derived table (i.e. subquery in the FROM clause), where you create the Porcentaje column.
SELECT TOP 5 dt.*,
CASE WHEN Porcentaje >= 75 THEN 'Elected'
WHEN Porcentaje >= 50 THEN 'Elected 1'
ELSE 'Not elected'
END AS Elections
FROM
(
select
(ROUND(Registered_Students/Total_Student * 100,2)) AS Porcentaje,
C.Total_Student, C.Registered_Students, S.Subject_Name, DATEPART(Year, C.Date) AS Año
FROM Cohort AS C
INNER JOIN Subject AS S
ON S.Id_Subject = C.Id_Subject
) dt
ORDER BY Porcentaje

Answer 4

The standard case syntax is
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;
You can fix your query by writing like this
Query will be easier to understand
Different indentation makes it easier to modify and to read
SELECT TOP 5
(ROUND(Registered_Students / Total_Student * 100, 2)) AS Porcentaje
, C.Total_Student
, C.Registered_Students
, S.Subject_Name
, DATEPART(YEAR, C.Date) AS Año,
(CASE
WHEN Porcentaje >= 75 THEN 'Elected'
WHEN Porcentaje >= 50 THEN 'Elected 1'
ELSE 'Not elected' END) AS Elections
FROM Cohort AS C
INNER JOIN Subject AS S
ON S.Id_Subject = C.Id_Subject
ORDER BY Porcentaje