Calculated column syntax when using a group by function Teradata - sql

Question

I'm trying to include a column calculated as a % of OTYPE.
IE
Order type | Status | volume of orders at each status | % of all orders at this status
SELECT
T.OTYPE,
STATUS_CD,
COUNT(STATUS_CD) AS STATVOL,
(STATVOL / COUNT(ROW_ID)) * 100
FROM Database.S_ORDER O
LEFT JOIN /* Finding definitions for status codes & attaching */
(
SELECT
ROW_ID AS TYPEJOIN,
"NAME" AS OTYPE
FROM database.S_ORDER_TYPE
) T
ON T.TYPEJOIN = ORDER_TYPE_ID
GROUP BY (T.OTYPE, STATUS_CD)
/*Excludes pending and pending online orders */
WHERE CAST(CREATED AS DATE) = '2018/09/21' AND STATUS_CD <> 'Pending'
AND STATUS_CD <> 'Pending-Online'
ORDER BY T.OTYPE, STATUS_CD DESC
OTYPE STATUS_CD STATVOL TOTALPERC
Add New Service Provisioning 2,740 100
Add New Service In-transit 13 100
Add New Service Error - Provisioning 568 100
Add New Service Error - Integration 1 100
Add New Service Complete 14,387 100
Current output just puts 100 at every line, need it to be a % of total orders
Could anyone help out a Teradata & SQL student?
The complication making this difficult is my understanding of the group by and count syntax is tenuous. It took some fiddling to get it displayed as I have it, I'm not sure how to introduce a calculated column within this combo.
Thanks in advance

Answer 1

There are a couple of places the total could be done, but this is the way I would do it. I also cleaned up your other sub query which was not required, and changed the date to a non-ambiguous format (change it back if it cases an issue in Teradata)
SELECT
T."NAME" as OTYPE,
STATUS_CD,
COUNT(STATUS_CD) AS STATVOL,
COUNT(STATUS_CD)*100/TotalVol as Pct
FROM database.S_ORDER O
LEFT JOIN EDWPRDR_VW40_SBLCPY.S_ORDER_TYPE T on T.ROW_ID = ORDER_TYPE_ID
cross join (select count(*) as TotalVol from database.S_ORDER) Tot
GROUP BY T."NAME", STATUS_CD, TotalVol
WHERE CAST(CREATED AS DATE) = '2018-09-21' AND STATUS_CD <> 'Pending' AND STATUS_CD <> 'Pending-Online'
ORDER BY T."NAME", STATUS_CD DESC

Answer 2

A where clause comes before a group by clause, so the query
shown in the question isn't valid.
Always prefix every column reference with the relevant table alias, below I have assumed that where you did not use the alias that it belongs to the orders table.
You probably do not need a subquery for this left join. While there are times when a subquery is needed or good for performance, this does not appear to be the case here.
Most modern SQL compliant databases provide "window functions", and Teradata does do this. They are extremely useful, and here when you combine count() with an over clause you can get the total of all rows without needing another subquery or join.
Because there is neither sample data nor expected result provided with the question I do not actually know which numbers you really need for your percentage calculation. Instead I have opted to show you different ways to count so that you can choose the right ones. I suspect you are getting 100 for each row because the count(status_cd) is equal to the count(row_id). You need to count status_cd differently to how you count row_id. nb: The count() function increases by 1 for every non-null value
I changed the way your date filter is applied. It is not efficient to change data on every row to suit constants in a where clause. Leave the data untouched and alter the way you apply the filter to suit the data, this is almost always more efficient (search sargable)
SELECT
t.OTYPE
, o.STATUS_CD
, COUNT(o.STATUS_CD) count_status
, COUNT(t.ROW_ID count_row_id
, count(t.row_id) over() count_row_id_over
FROM dbo.S_ORDER o
LEFT JOIN dbo.S_ORDER_TYPE t ON t.TYPEJOIN = o.ORDER_TYPE_ID
/*Excludes pending and pending online orders */
WHERE o.CREATED >= '2018-09-21' AND o.CREATED < '2018-09-22'
AND o.STATUS_CD <> 'Pending'
AND o.STATUS_CD <> 'Pending-Online'
GROUP BY
t.OTYPE
, o.STATUS_CD
ORDER BY
t.OTYPE
, o.STATUS_CD DESC

Answer 3

As #TomC already noted, there's no need for the join to a Derived Table. The simplest way to get the percentage is based on a Group Sum. I also changed the date to an Standard SQL Date Literal and moved the where before group by.
SELECT
t."NAME",
o.STATUS_CD,
Count(o.STATUS_CD) AS STATVOL,
-- rule of thumb: multiply first then divide, otherwise you will get unexpected results
-- (Teradata rounds after each calculation)
100.00 * STATVOL / Sum(STATVOL) Over ()
FROM database.S_ORDER AS O
/* Finding definitions for status codes & attaching */
LEFT JOIN database.S_ORDER_TYPE AS t
ON t.ROW_ID = o.ORDER_TYPE_ID
/*Excludes pending and pending online orders */
-- if o.CREATED is a Timestamp there's no need to apply the CAST
WHERE Cast(o.CREATED AS DATE) = DATE '2018-09-21'
AND o.STATUS_CD NOT IN ('Pending', 'Pending-Online')
GROUP BY (T.OTYPE, o.STATUS_CD)
ORDER BY T.OTYPE, o.STATUS_CD DESC
Btw, you probably don't need an Outer Join, Inner should return the same result.