Salary PAYE brackets using a stored procedure - sql-server

Question

I am trying to insert into an Employee table and I want the if statements to insert into the Salary, NetSalary, and Deduction columns if the Employee will earn a certain amount based on the hourly rate.
If statements are meant to insert data into the relevant column when the amount falls into a particular bracket
ALTER PROCEDURE [dbo].[spSaveEmployee]
(#EmployeePersonName Varchar(20),
#JobTitle int,
#Branch int,
#Department int,
#Manager int,
#HourlyRate MONEY,
#PaymentDate datetime = '2021-10-05 00:00:00.000',
#ErrorMessage Varchar(50) OUTPUT)
AS
BEGIN
DECLARE #DefaultDate DATETIME = GETDATE()
--DECLARE #PAYE INT
--SET #PAYE = 26 / 100
DECLARE #Salary INT
--SET #Salary = #HourlyRate * 180
--DECLARE #PYE INT
--SET #PYE = 1.15
DECLARE #NetSalary MONEY
DECLARE #Deduction DECIMAL (18,2)
DECLARE #NetSalary1 MONEY
DECLARE #NetSalary2 MONEY
DECLARE #NetSalary3 MONEY
--SET #NetSalary = #Salary - #PYE
DECLARE #Deduction1 DECIMAL (18,2)
DECLARE #Deduction2 DECIMAL (18,2)
DECLARE #Deduction3 DECIMAL (18,2)
SET #Deduction1 = (#Salary * 18) / 100
SET #NetSalary1 = #Salary - #Deduction1
SET #Deduction2 = (#Salary * 26) / 100
SET #NetSalary2 = #Salary - #Deduction2
SET #Deduction3 = (#Salary * 31) / 100
SET #NetSalary3 = #Salary - #Deduction3
IF NOT EXISTS (SELECT * FROM EmployeeBook
WHERE EmployeePersonName = #EmployeePersonName)
BEGIN
INSERT INTO EmployeeBook (EmployeePersonName, JobTitle, Branch, Department,
Manager, HourlyRate, PAYE_Tax, Salary,
NetSalary, PaymentDate, Deductions)
VALUES (#EmployeePersonName, #JobTitle, #Branch, #Department,
#Manager, #HourlyRate, 1.15, #Salary,
#NetSalary, #DefaultDate, #Deduction)
SET #ErrorMessage = ''
IF #Salary <= 321000
BEGIN
SELECT #Deduction = #Deduction
SELECT #NetSalary = #NetSalary
END
ELSE IF #Salary >= 321001 AND #Salary <= 445100
BEGIN
SELECT #Deduction = #Deduction2
SELECT #NetSalary = #NetSalary2
END
ELSE IF #Salary >= 445100 AND #Salary <= 584200
BEGIN
SELECT #Deduction = #Deduction3
SELECT #NetSalary = #NetSalary3
END
END
ELSE
BEGIN
SET #EmployeePersonName = ''
SET #JobTitle = 0
SET #Branch = 0
SET #Department = 0
SET #Manager = 0
SET #HourlyRate = 0.00
SET #Salary = 0.00
SET #NetSalary = 0.00
SET #PaymentDate = #DefaultDate
SET #Deduction = 0
SET #ErrorMessage = 'Sorry could not save ' + #EmployeePersonName + ' Employee name already exists'
END
END
GO

Answer 1

The following does what I believe you are trying to accomplish. Issues and comments:
You set your variables after you use them - so they have no effect.
T-SQL is optimised for set-based operations therefore you should attempt to carry out your operations in a set-based manner if possible rather than procedural
Best practice is to use consistent casing for T-SQL
As Larnu points out, error handling is best handled using throw.
Best practice is to always schema prefix your database objects
SPs should always have a return statement
SPs should normally start SET NOCOUNT, XACT_ABORT ON;
Since you can validate the existence of the person straight away, I would and save any further processing time.
What if the salary falls outside the defined brackets? You might not expect it, but you should handle it hence the ELSE in the CASE expression.
I would avoid prefixing your SP's with sp as its too close to the system prefix sp_. In fact why prefix them at all?
When creating brackets like this, one end condition needs to be less than or equal and the other condition greater than (or vice-versa) to avoid a value falling into 2 brackets. Even though the case will short-circuit to the first matching expression, its best from an understanding perspective to have correct and accurate logic.
ALTER PROCEDURE [dbo].[SaveEmployee]
(
#EmployeePersonName VARCHAR(20),
#JobTitle INT,
#Branch INT,
#Department INT,
#Manager INT,
#HourlyRate MONEY,
#PaymentDate DATETIME = '2021-10-05 00:00:00.000',
#ErrorMessage VARCHAR(50) OUTPUT
)
AS
BEGIN
SET NOCOUNT, XACT_ABORT ON;
IF EXISTS (SELECT 1 FROM dbo.EmployeeBook WHERE EmployeePersonName = #EmployeePersonName) BEGIN
SET #ErrorMessage = 'Sorry could not save ' + #EmployeePersonName + ' Employee name already exists' END
RETURN;
-- Comment out 2 lines above to uncomment the 2 code line below
-- As suggested by Larnu, this would be more a typical error handling approach
--DECLARE #Error NVARCHAR(2048) = 'Sorry could not save ' + #EmployeePersonName + ' Employee name already exists';
--THROW 51000, #Error, 1;
END;
DECLARE #DefaultDate DATETIME = GETDATE(), #Salary INT = #HourlyRate * 180;
INSERT INTO dbo.EmployeeBook (EmployeePersonName, JobTitle, Branch, Department
, Manager, HourlyRate, PAYE_Tax, Salary
, NetSalary, PaymentDate, Deductions)
SELECT EmployeePersonName, JobTitle, Branch, Department
, Manager, HourlyRate, 1.15, Salary
, CASE SalaryBracket WHEN 1 THEN Salary - Deduction1
WHEN 2 THEN Salary - Deduction2
WHEN 3 THEN Salary - Deduction3
-- ELSE ??
END
, #DefaultDate
, CASE SalaryBracket WHEN 1 THEN Deduction1
WHEN 2 THEN Deduction2
WHEN 3 THEN Deduction3
-- ELSE ??
END
FROM (
VALUES (#EmployeePersonName, #JobTitle, #Branch, #Department, #Manager, #HourlyRate, 1.15, #Salary
, (#Salary * 18) / 100, (#Salary * 26) / 100, (#Salary * 31) / 100
-- Compute Salary Bracket in one place for reuse
, CASE WHEN #Salary <= 321000 THEN 1
WHEN #Salary > 321001 AND #Salary <= 445100 THEN 2
WHEN #Salary > 445100 AND #Salary <= 584200 THEN 3 END
)
) AS X (EmployeePersonName, JobTitle, Branch, Department, Manager, HourlyRate, PAYE_Tax, Salary, Deduction1, Deduction2, Deduction3, SalaryBracket);
RETURN 0;
END
GO