Select from a Temp table is giving slow performance - sql

Question

I need some help with the below query where the last step of
Select * from #PersonDetail order by....
is taking so long to execute - why?
There are millions of records being inserted in this temp table #PersonDetail and insert process takes a few seconds, but the last Select from this same temp table is taking so long.
I created a unique clustered index on the columns used for order by and tried many other options but it doesn't make any difference in the performance.
It is a big stored procedure with many temp table but it is this last select step which is impacting the performance. Here is an example of the last step of the query:
DROP TABLE IF EXISTS #PersonDetail
CREATE TABLE #PersonDetail
(
PersonId INT NOT NULL,
Name NVARCHAR(50) NULL,
Number INT NOT NULL,
Tag NVARCHAR(50) NULL,
UserId INT NOT NULL,
NumberEncrypted VARCHAR(100),
Type NVARCHAR(255),
Status NVARCHAR(50),
CreatedDate DATETIMEOFFSET(7),
AddressDetailId NVARCHAR(50),
Category NVARCHAR(50),
PrimaryId INT,
DailyAmount MONEY,
UNIQUE (PersonId UserId),
UNIQUE CLUSTERED(CreatedDate, UserId)
)
INSERT INTO #PersonDetail (PersonId, Name, Number, Tag, UserId, NumberEncrypted,
Type, Status, CreatedDate, AddressDetailId, Category, PrimaryId, Amount)
SELECT
PersonId, Name, Number, Tag, UserId, NumberEncrypted,
Type, Status, CreatedDate, AddressDetailId, Category, PrimaryId, DailyAmount
FROM
#User u
JOIN
dbo.DailyAmount da (NOLOCK) ON da.UserId = u.UserId
SELECT *
FROM #PersonDetail pd
ORDER BY CreatedDate, UserId

Answer 1

You must specify what database are you using.
In general, you must do theese things:
create some indexes on the join columns (DailyAmount.userId, User.userID); how to create the index must change;
create an index on the order by columns, (CreatedDate+UserID); this must change, in postgresql for example an index with the 2 column is better than 2 indexes;
If your data are not changing frequently, you could try materialized view and create the indexes on the materialized view.