Sql Dynamic Order by Using Alias

SQL dynamic ORDER BY using alias

Column aliases defined in the SELECT can only be used in the ORDER BY on their own. Not in an expression.

You can adjust your original attempt as follows.

;WITH T
AS (SELECT u.FirstName + ' ' + u.LastName AS PhysicianName,
COUNT(r.Id) AS ReferralsCount
FROM Referrals r
INNER JOIN Users u
ON r.PhysicianId = u.Id
GROUP BY r.PhysicianId,
u.FirstName,
u.LastName)
SELECT *
FROM T
ORDER BY CASE
WHEN @orderby = 'PhysicianName' THEN PhysicianName
END,
CASE
WHEN @orderby = 'ReferralsCount' THEN ReferralsCount
END

Dynamic Order By clause with column and sort information coming from a table?

This will only work if you are using dynamic SQL. I was not able to get it to work as-is.

ORDER BY clause is not sorting by alias in SQL Server

You have the column UserName and an alias UserName. It is the column value that is being used to sort the results, not the alias. While it is perfectly acceptable to use an alias name inside the ORDER BY clause, it cannot be used inside CASE WHEN statement.

The solution is to use a sub-query (or CTE):

DECLARE
@Sortorder VARCHAR(5) = 'asc',
@ColumnNumber INT = 9

SELECT * FROM (
SELECT SUBSTRING(csu.UserName, /* removed for readability */) AS UserNameCopy, w.WorkItemId
FROM [tasks].[WorkItems] w
LEFT JOIN operations.CustomerServiceUser csu ON csu.UserId = w.AssignedToUserId
WHERE w.[ShowInTaskList] = 1 AND UserName IS NOT NULL
) AS SubQuery
ORDER BY
CASE WHEN @ColumnNumber = 9 AND @SortOrder = 'asc' THEN SubQuery.UserNameCopy END ASC,
CASE WHEN @ColumnNumber = 9 AND @SortOrder = 'desc' THEN SubQuery.UserNameCopy END DESC

ORDER BY with a CASE statement for column with alias

Try this

ORDER BY 
CASE WHEN @sortColumnName = 'LastPayCheckDate' AND @sortDirection = 'ASC'
THEN MAX(PayCheckDate) END ASC,
CASE WHEN @sortColumnName = 'LastPayCheckDate' AND @sortDirection = 'DESC'
THEN MAX(PayCheckDate) END DESC

Example

create table Test (id int, somevalue int)

insert Test values(1,1)
insert Test values(2,1)
insert Test values(3,2)
insert Test values(3,2)
insert Test values(4,2)

run this in 1 shot

declare @sortDirection char(4)
select @sortDirection = 'DESC'

select somevalue, COUNT(*)
from Test
group by somevalue
order by case when @sortDirection = 'ASC'
then COUNT(*) end asc,
case when @sortDirection = 'DESC'
then COUNT(*) end desc

select @sortDirection = 'ASC'
select somevalue, COUNT(*)
from Test
group by somevalue
order by case when @sortDirection = 'ASC'
then COUNT(*) end asc,
case when @sortDirection = 'DESC'
then COUNT(*) end desc

dynamic alias in sql server

Approach without dynamic SQL:

--I create temp table for demonstration
DECLARE @some_table TABLE (
Something int,
EmpCode INT
)

INSERT INTO @some_table (Something, EmpCode)
VALUES (1, 10),(1, 22),(1, 12),(2, 12),(2, 30),(3, 65),(3, 15),(3, 11),(3, 5)

--Declare parameter we want to search
DECLARE @param int = 1

--Query
--In cte we select what we need based on parameter
;WITH cte AS (
SELECT 'CountEmp'+CAST(@param as nvarchar(10)) as SomeThing,
CAST(COUNT(EmpCode) as nvarchar(10)) as EmpCodeCount,
ROW_NUMBER() OVER (ORDER BY SomeThing ) as rn
FROM @some_table
WHERE SomeThing = @param
GROUP BY SomeThing
)
--And here comes UNION
SELECT SomeThing as Result
FROM (
SELECT SomeThing,rn
FROM cte
UNION ALL
SELECT EmpCodeCount ,rn
FROM cte
) as t
ORDER BY rn, SomeThing DESC

Output:

Result
------------------
CountEmp1
3

(2 row(s) affected)

Dynamic column alias from another column value in SELECT

It seems that there is no way to create the column alias dynamically without knowing the values since the beginning. As many commented the only way to achieve this kind of "table re-mapping" is to use the crosstab function.

Crosstab function summary

This function takes 2 arguments:

  • The first one is a SQL statement that must return 3 columns:
    • The first column contains the values identifying each instance and that must be grouped in order to get the final result.
    • The second column contains the values that are used as categories in the final pivot table: each value will create a separate column.
    • The third column contains the values used to compile the new columns formed: for each category this column has the value of the instance that had the category value in the original table.
  • The second argument is not mandatory and is a SQL statement that returns the distinct values the function should use as categories.

Example

In the example above we must pass a query to crosstab that:

  • Returns as the first column the identifier of each final instance (in this case id)
  • As second column the values used as categories (all values in key)
  • As third column the values used to fill the categories (all values in value)

So the final query should be:

select * from crosstab(
'select "id", "key", "value" from testTable order by 1, 2;',
'select distinct "key" from testTable order by 1;'
) as result ("id" int8, "a" text, "b" text);

Since the crosstab function requires a column definition for the final pivot table, there is no way to determine the column alias dynamically.

Dynamically infer column names with client

A possible way to do that, with a PostgreSQL client, is to launch the second query we passed as argument to crosstab in order to retrieve the final columns and then infer the final crosstab query.

As an example, with pseudo-javascript:

const client;

const aliases = client.query(`select distinct "key" from testTable order by 1;`);

const finalTable = client.query(`select * from crosstab(
'select "id", "key", "value" from testTable order by 1, 2;',
'select distinct "key" from testTable order by 1;'
) as result ("id" int8, ${aliases.map(v => v + ' data_type').join(',')});`)

Useful articles

https://learnsql.com/blog/creating-pivot-tables-in-postgresql-using-the-crosstab-function/

Dynamic Aliases in the SQL statement

I'm not sure if you can add dynamic aliases, but you should be able to do something like this (if you have only a few possible aliases):

SELECT
CASE P.Type WHEN 'Individual' THEN P.Amount ELSE NULL END AS Salary,
CASE P.Type WHEN 'Individual' THEN NULL ELSE P.Amount END AS Profit
FROM
Person p


Related Topics



Leave a reply



Submit