Select which value is greater based on two different columns

Question

I would like to select which rate is greater and enter it in a single query result based on the results of a UNION ALL. For example employee 200 makes 25 dollars as a base rate per hour but the job he works on has a base rate of 10.00. He should be getting 25.00 per hour then. Employee 100 has a base rate of 10.00 but the job's base rate is 25.00. So he should get 25.00 per hour as well. I would like to select the highest rate for each employee. Something similar to this idea. SELECT EmployeeID, RATE_A or RATE_B from .... Here is some data I put together

 CREATE Table WageRate(
[ID] [int] IDENTITY(1,1) NOT NULL,
[RateCode] int NULL,
[Rate] Decimal (10,2) NULL
)

INSERT INTO WageRate( RateCode,Rate)
Values (1,10.00), (2,15.00), (3,20.00), (4,25.00)

Create Table Employee(
[ID] [int] IDENTITY(1,1) NOT NULL,
[EmployeeID] int NULL,
[RateCode] int NULL
)

 Insert Into Employee (EmployeeID,RateCode)
 Values (100,1), (200,4)

 Create Table TimeCards(
[ID] [int] IDENTITY(1,1) NOT NULL,
[EmployeeID] int NULL,
[Hours] Decimal (10,2) NULL,
[JobRateCode] int NULL
 )

 Insert Into TimeCards (EmployeeID,[Hours],JobRateCode)
 Values (100,8.00,4), (200,8.00,1)


SELECT t1.Employeeid ,(t0.Rate) as [Rate_A] ,Null FROM WageRate t0 
 INNER JOIN Employee t1 ON t1.RateCode= t0.RateCode
 INNER JOIN TimeCards t2 on t1.EmployeeID = t2.EmployeeID

UNION ALL

SELECT t4.Employeeid ,Null,(t3.Rate) As [Rate_B] FROM WageRate t3 
 INNER JOIN TimeCards t4 on t4.JobRateCode = t3.RateCode
 INNER JOIN Employee t5 ON t4.EmployeeID= t5.EmployeeID

Answer 1

Using a case expression you can do it with a single query without a union:

SELECT  e.EmployeeID, 
        CASE WHEN ISNULL(ew.Rate, 0.0) > ISNULL(jw.Rate, 0.0) THEN 
            ew.Rate 
        ELSE 
            jw.Rate 
        END As Rate
FROM Employee e
LEFT JOIN TimeCards t On e.EmployeeID = t.EmployeeID
LEFT JOIN WageRate ew ON e.RateCode = ew.RateCode
LEFT JOIN WageRate jw ON t.JobRateCode = jw.RateCode

See a live demo on rextester.

Answer 2

SELECT e.employeeid,
CASE 
    WHEN wr_tc.rate > wr_emp.rate
        THEN wr_tc.rate
    ELSE wr_emp.rate
    END AS rate
FROM Employee e
INNER JOIN wagerate wr_emp ON wr_emp.ratecode = e.RateCode
INNER JOIN timecards tc ON tc.employeeid = e.employeeid
INNER JOIN wagerate wr_tc ON wr_tc.RateCode = tc.jobratecode

Answer 3

How about something like this...

 SELECT 
    e.EmployeeID,
    tc.Hours,
    PayRate = CASE WHEN wr1.Rate > wr2.Rate THEN wr1.Rate ELSE wr2.Rate END,
    TotalPay = tc.Hours * CASE WHEN wr1.Rate > wr2.Rate THEN wr1.Rate ELSE wr2.Rate END
 FROM 
    #Employee e
    JOIN #WageRate wr1
        ON e.RateCode = wr1.RateCode
    JOIN #TimeCards tc
        ON e.EmployeeID = tc.EmployeeID
    JOIN #WageRate wr2
        ON tc.JobRateCode = wr2.RateCode;

Results...

EmployeeID  Hours                                   PayRate                                 TotalPay
----------- --------------------------------------- --------------------------------------- ---------------------------------------
200         8.00                                    25.00                                   200.0000
100         8.00                                    25.00                                   200.0000

Answer 4

To do this without CASE logic:

SQL Fiddle

Query:

SELECT s.EmployeeID, s.Hours, s.jobRate, s.wageRate
  , ( SELECT max(r) FROM (VALUES (s.jobRate),(s.wageRate)) AS value(r)) AS maxRate
FROM (
  SELECT e.EmployeeID, t.Hours
      , COALESCE(w1.Rate,0) AS jobRate
      , COALESCE(w2.Rate,0) AS wageRate
  FROM TimeCards t
  INNER JOIN Employee e ON t.EmployeeID = e.EmployeeID
     LEFT OUTER JOIN WageRate w1 ON e.RateCode = w1.RateCode          
  LEFT OUTER JOIN WageRate w2 ON t.jobRateCode = w2.RateCode
) s
;

Results:

| EmployeeID | Hours | jobRate | wageRate | maxRate |
|------------|-------|---------|----------|---------|
|        100 |     8 |      10 |       25 |      25 |
|        200 |     8 |      25 |       10 |      25 |