TSQL Select only the highest credentail - sql

Question

I have a query that is returning multiple line for a single service because an individual may have multiple credentials. In the medical field you retain several credentials but for simplicity sake I will use just standard credentials Phd, MA, MS, BA, BS, AS
I need to know the simplest way to ignore rows where Z_ServiceLedger.clientvisit_id has any Credentials.credentials lower in the hierarchy. So if an employee does a service and he has a Phd and a MA only return the lines for Phd and if he has a Phd an Ma and a BA only return the lines for phd. We have around 50 credentials so if I use CASE for each credential you can see how mess that will get an I'm hoping there is a better way to avoid that.
Here is my current query:
SELECT DISTINCT
SUM(CASE WHEN v.non_billable = 0 THEN v.duration ELSE 0 END) / 60 AS billable_hours,
SUM(CASE WHEN (v.non_billable = 0 AND Z_ServiceLedger.payer_id = 63) THEN v.duration ELSE 0 END) / 60 AS billable_mro_hours,
Credentials.credentials
FROM
Z_ServiceLedger
INNER JOIN
ClientVisit v ON Z_ServiceLedger.clientvisit_id = v.clientvisit_id
LEFT JOIN
Employees ON v.emp_id = Employees.emp_id
LEFT JOIN
EmployeeCredential ON Employees.emp_id = EmployeeCredential.emp_id
LEFT JOIN
Credentials ON Credentials.credential_id = EmployeeCredential.credential_id
WHERE
v.rev_timein <= CASE
WHEN EmployeeCredential.end_date IS NOT NULL
THEN EmployeeCredential.end_date
ELSE GETDATE()
END
AND v.rev_timein >= #param1
AND v.rev_timein < DateAdd(d, 1, #param2)
AND Z_ServiceLedger.amount > 0
AND v.splitprimary_clientvisit_id IS NULL
AND v.gcode_primary_clientvisit_id IS NULL
AND v.non_billable = 0
AND v.non_billable = 'FALSE'
AND v.duration / 60 > 0
AND Z_ServiceLedger.action_type NOT IN ('SERVICE RATE CHANGE', 'CLIENT STATEMENT')
AND (EmployeeCredential.is_primary IS NULL OR EmployeeCredential.is_primary != 'False')
AND v.client_id != '331771 '
GROUP BY
Credentials.credentials,
v.non_billable
ORDER BY
Credentials.credentials

Answer 1

Some aliases and formatting really shed some light on some major logical flaws here. You have at least two predicates in your where clause that logically turn a left join into an inner join. This is total shot in the dark since from both of your questions today we don't have anything to actually work with for tables or sample data.
The biggest concern though is your where clause is trying to get rows v.non_billable = 0 and where it equals 'FALSE'. It can't be both.
Select sum(Case When v.non_billable = 0 Then v.duration Else 0 End) / 60 As billable_hours
, sum(Case When (v.non_billable = 0 And sl.payer_id = 63) Then v.duration Else 0 End) / 60 As billable_mro_hours
, c.credentials
From Z_ServiceLedger sl
Inner Join ClientVisit v On sl.clientvisit_id = v.clientvisit_id
Left Join Employees e On v.emp_id = e.emp_id
Left Join EmployeeCredential ec On e.emp_id = ec.emp_id
--if you leave these predicates in the where clause you have turned your left join into an inner join.
AND v.rev_timein <= isnull(ec.end_date, GetDate())
and (ec.is_primary Is Null Or ec.is_primary != 'False')
Left Join Credentials c On c.credential_id = ec.credential_id
Where v.rev_timein >= #param1
And v.rev_timein < DateAdd(day, 1, #param2)
And v.splitprimary_clientvisit_id Is Null
And v.gcode_primary_clientvisit_id Is Null
--you need to pick one value for v.non_billable. It can't be both 0 and 'FALSE' at the same time.
And v.non_billable = 0
And v.non_billable = 'FALSE'
--And v.duration / 60 > 0
and v.duration > 60 --this is the same thing and is SARGable
And sl.amount > 0
And sl.action_type NOT IN ('SERVICE RATE CHANGE', 'CLIENT STATEMENT')
And v.client_id != '331771 '
Group By c.credentials
, v.non_billable
Order By c.credentials

Answer 2

EDIT: Modified query to add a CTE to calculate the credential_rank, using a FROM (VALUES (...)) table-value-constructor syntax. This works in SQL 2008+. (https://learn.microsoft.com/en-us/sql/t-sql/queries/table-value-constructor-transact-sql?view=sql-server-2017)
SQL Fiddle
First, I'll build out a very simple piece of data.
SETUP:
CREATE TABLE Employees ( emp_id int, emp_name varchar(20) ) ;
INSERT INTO Employees (emp_id, emp_name)
VALUES (1,'Jay'),(2,'Bob')
;
CREATE TABLE Credentials ( credential_id int, credentials varchar(20), credential_rank int ) ;
INSERT INTO Credentials (credential_id, credentials, credential_rank)
VALUES (1,'BA',3),(2,'MA',2),(3,'PhD',1)
;
CREATE TABLE EmployeeCredential (emp_id int, credential_id int, is_primary bit, end_date date )
INSERT INTO EmployeeCredential (emp_id, credential_id, is_primary, end_date)
VALUES
( 1,2,null,'20200101' )
, ( 1,3,0,'20200101' ) /* NON-PRIMARY */
, ( 1,1,1,'20100101' ) /* EXPIRED CRED */
, ( 2,3,null,'20200101' )
, ( 2,3,1,'20200101' )
;
CREATE TABLE z_ServiceLedger ( payer_id int, clientvisit_id int, amount int, action_type varchar(50) ) ;
INSERT INTO z_ServiceLedger ( payer_id, clientvisit_id, amount, action_type )
VALUES (63,1,10,'XXXXX'),(63,2,20,'XXXXX'),(63,3,10,'XXXXX'),(63,4,30,'XXXXX')
;
CREATE TABLE ClientVisit ( clientvisit_id int, client_id int, non_billable bit, duration int, emp_id int , rev_timein date, splitprimary_clientvisit_id int, gcode_primary_clientvisit_id int ) ;
INSERT INTO ClientVisit ( clientvisit_id, client_id, non_billable, duration, emp_id, rev_timein, splitprimary_clientvisit_id, gcode_primary_clientvisit_id )
VALUES
(1, 1234, 0, 110, 1, getDate(), null, null )
, (2, 1234, null, 120, 1, getDate(), null, null )
, (3, 1234, 1, 110, 2, getDate(), null, null )
, (4, 1234, 0, 130, 2, getDate(), null, null )
;
MAIN QUERY:
; WITH creds AS (
SELECT c.credential_id, c.credentials, r.credential_rank
FROM Credentials c
LEFT OUTER JOIN (VALUES (1,3),(2,2),(3,1) ) r(credential_id, credential_rank)
ON c.credential_id = r.credential_id
)
SELECT DISTINCT
SUM(CASE WHEN ISNULL(v.non_billable,1) = 0 THEN v.duration ELSE 0 END)*1.0 / 60 AS billable_hours,
SUM(CASE WHEN (ISNULL(v.non_billable,1) = 0 AND zsl.payer_id = 63) THEN v.duration ELSE 0 END)*1.0 / 60 AS billable_mro_hours,
s2.credentials
FROM Z_ServiceLedger zsl
INNER JOIN ClientVisit v ON zsl.clientvisit_id = v.clientvisit_id
AND v.rev_timein >= #param1
AND v.rev_timein < DateAdd(d, 1, #param2)
AND v.splitprimary_clientvisit_id IS NULL
AND v.gcode_primary_clientvisit_id IS NULL
AND ISNULL(v.non_billable,1) = 0
AND v.duration*1.0 / 60 > 0
AND v.client_id <> 331771
INNER JOIN (
SELECT s1.emp_id, s1.emp_name, s1.credential_id, s1.credentials, s1.endDate
FROM (
SELECT e.emp_id, e.emp_name, c.credential_id, c.credentials, ISNULL(ec.end_date,GETDATE()) AS endDate
, ROW_NUMBER() OVER (PARTITION BY e.emp_id ORDER BY c.credential_rank) AS rn
FROM Employees e
LEFT OUTER JOIN EmployeeCredential ec ON e.emp_id = ec.emp_id
AND ISNULL(ec.is_primary,1) <> 0 /* I don't think a NULL is_primary should be TRUE */
LEFT OUTER JOIN creds c ON ec.credential_id = c.credential_id
) s1
WHERE s1.rn = 1
) s2 ON v.emp_id = s2.emp_id
AND v.rev_timein <= s2.endDate /* Credential not expired at rev_timein */
WHERE zsl.amount > 0
AND zsl.action_type NOT IN ('SERVICE RATE CHANGE', 'CLIENT STATEMENT')
GROUP BY s2.credentials
ORDER BY s2.credentials
Results:
| billable_hours | billable_mro_hours | credentials |
|----------------|--------------------|-------------|
| 1.833333 | 1.833333 | MA |
| 2.166666 | 2.166666 | PhD |
A couple of things to watch for:
1) Integer Division : duration/60 will return an integer. So if you had duration=70, then you'd have 70/60 = 1. You'd miss that 10 minutes, because of the result will be converted back to an integer. You lose that extra 10 minutes. Probably not what you inteded. The easiest solution is to just multiply duration by 1.0 so that it is forced into a decimal datatype and won't cause the operation to be treated like integers.
2) EmployeeCredential.is_primary != 'False' : Rather than account for the strings of "True"/"False", you should use an actual boolean value (1/0). And a NULL value should indicate that the value is NOT TRUE or FALSE rather than implying TRUE. Also, in SQL, != will work to indicate NOT EQUAL TO, but you should use <> instead. It means the same thing, but is grammatically more correct for SQL.
3) v.non_billable = 0 AND v.non_billable = 'FALSE' : This can be shortened to ISNULL(v.non_billable,1)=0 to short-circuit both checks, especially since non_billable can be NULL. You also avoid the implicit type converstion when comparing the number 0 and the string 'False'.
4) v.client_id != '331771 ' : Change to v.client_id<>33171. First, the != to <> that I mentioned earlier. Then '331771' is implicitly converted to a number. You should avoid implicit conversions.
5) You originally had v.non_billable in your GROUP BY. Since you aren't including it in your SELECT, you can't use it to GROUP BY. Also, you're already filtering out everything other than non_billable=0, so you'd never have more than one value to GROUP BY anyway. Just exclude it.
6) CASE WHEN EmployeeCredential.end_date IS NOT NULL THEN EmployeeCredential.end_date ELSE GETDATE() END : This is the same as saying ISNULL(EmployeeCredential.end_date,GETDATE()).
7) Unless you actually need to filter out specific records for a specific reason, more your JOIN conditions into the JOIN rather than using them in the WHERE clause. This will help you be more efficient with the data your initial query returns before it is filtered or reduced. Also, when using a WHERE filter with a LEFT JOIN, you may end up with unexpected results.