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ewdlop merged 1 commit into from
May 29, 2025
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Update company.tsql #47

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366 changes: 365 additions & 1 deletion T-Sql/company.tsql
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Original file line number Diff line number Diff line change
Expand Up @@ -167,7 +167,9 @@ VALUES (501, 3, '2023-12-15', 4.5, 1, 'Excellent performance in sales targets. G
INSERT INTO PERFORMANCE_REVIEW(reviewId, empId, reviewDate, rating, reviewerEmpId, comments)
VALUES (502, 6, '2023-12-16', 4.2, 1, 'Consistently meets targets. Could improve on documentation.');


-- ========================================
-- SELECT QUERIES
-- ========================================
-- Sample queries
-- Find all employees in Sales department
SELECT * FROM EMPLOYEE WHERE dept = 'Sales';
Expand All @@ -191,3 +193,365 @@ FROM EMPLOYEE e
LEFT JOIN ATTENDANCE a ON e.empId = a.empId
WHERE MONTH(a.workDate) = MONTH(GETDATE()) AND YEAR(a.workDate) = YEAR(GETDATE())
GROUP BY e.name;
-- ========================================
-- ALTER TABLE / UPDATE COLUMN TYPE QUERIES
-- ========================================

-- Increase the size of varchar columns
ALTER TABLE DEPARTMENT ALTER COLUMN deptName VARCHAR(50);
ALTER TABLE DEPARTMENT ALTER COLUMN location VARCHAR(100);

-- Change email column to accommodate longer email addresses
ALTER TABLE EMPLOYEE ALTER COLUMN email VARCHAR(100);

-- Expand project name and status fields
ALTER TABLE PROJECT ALTER COLUMN projectName VARCHAR(100);
ALTER TABLE PROJECT ALTER COLUMN status VARCHAR(25);

-- Increase performance review comments field
ALTER TABLE PERFORMANCE_REVIEW ALTER COLUMN comments VARCHAR(1000);

-- Add new columns to existing tables
ALTER TABLE EMPLOYEE ADD isActive BIT DEFAULT 1;
ALTER TABLE EMPLOYEE ADD terminationDate DATE NULL;

ALTER TABLE PROJECT ADD projectManager INT NULL;
ALTER TABLE PROJECT ADD FOREIGN KEY (projectManager) REFERENCES EMPLOYEE(empId);

ALTER TABLE DEPARTMENT ADD budget DECIMAL(15,2) NULL;

-- For SQL Server, to change data type of a column with data:
-- First, create a new column with the desired type
ALTER TABLE PROJECT_ASSIGNMENT ADD hoursAllocatedNew DECIMAL(7,2);
-- Copy data from old column to new column
UPDATE PROJECT_ASSIGNMENT SET hoursAllocatedNew = hoursAllocated;
-- Drop the old column
ALTER TABLE PROJECT_ASSIGNMENT DROP COLUMN hoursAllocated;
-- Rename the new column to the original name
EXEC sp_rename 'PROJECT_ASSIGNMENT.hoursAllocatedNew', 'hoursAllocated', 'COLUMN';


-- ========================================
-- COMPLEX SELECT QUERIES WITH CTEs
-- ========================================

-- 1. Employee Hierarchy with Recursive CTE
WITH EmployeeHierarchy AS (
-- Anchor member: Top-level managers
SELECT empId, name, managerId, jobTitle, 0 as Level
FROM EMPLOYEE
WHERE managerId IS NULL

UNION ALL

-- Recursive member: Employees under managers
SELECT e.empId, e.name, e.managerId, e.jobTitle, eh.Level + 1
FROM EMPLOYEE e
INNER JOIN EmployeeHierarchy eh ON e.managerId = eh.empId
)
SELECT empId, name, jobTitle, Level,
REPLICATE(' ', Level) + name AS HierarchicalName
FROM EmployeeHierarchy
ORDER BY Level, name;


-- 2. Department Performance Analysis with Multiple CTEs
WITH DeptSalary AS (
SELECT d.deptId, d.deptName,
AVG(s.amount) as avgSalary,
MIN(s.amount) as minSalary,
MAX(s.amount) as maxSalary,
COUNT(e.empId) as empCount
FROM DEPARTMENT d
JOIN EMPLOYEE e ON d.deptId = e.deptId
JOIN SALARY s ON e.empId = s.empId
GROUP BY d.deptId, d.deptName
),
DeptProjects AS (
SELECT d.deptId,
COUNT(DISTINCT p.projectId) as projectCount,
SUM(p.budget) as totalBudget,
AVG(p.budget) as avgProjectBudget
FROM DEPARTMENT d
LEFT JOIN PROJECT p ON d.deptId = p.deptId
GROUP BY d.deptId
)
SELECT ds.deptName,
ds.empCount,
ds.avgSalary,
ds.minSalary,
ds.maxSalary,
COALESCE(dp.projectCount, 0) as projectCount,
COALESCE(dp.totalBudget, 0) as totalProjectBudget,
COALESCE(dp.avgProjectBudget, 0) as avgProjectBudget
FROM DeptSalary ds
LEFT JOIN DeptProjects dp ON ds.deptId = dp.deptId
ORDER BY ds.avgSalary DESC;


-- 3. Employee Workload Analysis
WITH EmployeeProjects AS (
SELECT e.empId, e.name, e.deptId,
COUNT(pa.projectId) as projectCount,
SUM(pa.hoursAllocated) as totalHours
FROM EMPLOYEE e
LEFT JOIN PROJECT_ASSIGNMENT pa ON e.empId = pa.empId
GROUP BY e.empId, e.name, e.deptId
),
ProjectDetails AS (
SELECT pa.empId,
STRING_AGG(p.projectName, ', ') as projectList
FROM PROJECT_ASSIGNMENT pa
JOIN PROJECT p ON pa.projectId = p.projectId
GROUP BY pa.empId
)
SELECT ep.name,
d.deptName,
ep.projectCount,
ep.totalHours,
pd.projectList,
CASE
WHEN ep.totalHours > 40 THEN 'Overallocated'
WHEN ep.totalHours BETWEEN 30 AND 40 THEN 'Fully Allocated'
WHEN ep.totalHours BETWEEN 15 AND 29 THEN 'Partially Allocated'
ELSE 'Underallocated'
END as AllocationStatus
FROM EmployeeProjects ep
JOIN DEPARTMENT d ON ep.deptId = d.deptId
LEFT JOIN ProjectDetails pd ON ep.empId = pd.empId
ORDER BY ep.totalHours DESC;


-- 4. Salary Ranking within Departments
WITH SalaryRanking AS (
SELECT e.empId, e.name, d.deptName, s.amount,
RANK() OVER (PARTITION BY d.deptId ORDER BY s.amount DESC) as salaryRank,
DENSE_RANK() OVER (PARTITION BY d.deptId ORDER BY s.amount DESC) as denseRank,
ROW_NUMBER() OVER (PARTITION BY d.deptId ORDER BY s.amount DESC) as rowNum,
PERCENT_RANK() OVER (PARTITION BY d.deptId ORDER BY s.amount DESC) as percentRank
FROM EMPLOYEE e
JOIN DEPARTMENT d ON e.deptId = d.deptId
JOIN SALARY s ON e.empId = s.empId
)
SELECT name, deptName, amount,
salaryRank,
CASE
WHEN percentRank <= 0.25 THEN 'Top 25%'
WHEN percentRank <= 0.50 THEN 'Top 50%'
WHEN percentRank <= 0.75 THEN 'Top 75%'
ELSE 'Bottom 25%'
END as SalaryPercentile
FROM SalaryRanking
ORDER BY deptName, salaryRank;


-- 5. Project Timeline Analysis
WITH ProjectStatus AS (
SELECT projectId, projectName,
startDate, endDate, budget, status,
DATEDIFF(day, startDate, endDate) as durationDays,
DATEDIFF(day, startDate, GETDATE()) as daysElapsed,
CASE
WHEN endDate < GETDATE() AND status != 'Completed' THEN 'Overdue'
WHEN endDate >= GETDATE() AND status = 'In Progress' THEN 'On Track'
WHEN status = 'Completed' THEN 'Completed'
ELSE 'Not Started'
END as ProjectHealth
FROM PROJECT
),
ProjectTeam AS (
SELECT p.projectId,
COUNT(DISTINCT pa.empId) as teamSize,
SUM(pa.hoursAllocated) as totalAllocatedHours
FROM PROJECT p
LEFT JOIN PROJECT_ASSIGNMENT pa ON p.projectId = pa.projectId
GROUP BY p.projectId
)
SELECT ps.projectName,
ps.status,
ps.ProjectHealth,
ps.durationDays,
ps.daysElapsed,
CAST(ps.daysElapsed * 100.0 / NULLIF(ps.durationDays, 0) AS DECIMAL(5,2)) as PercentComplete,
ps.budget,
pt.teamSize,
pt.totalAllocatedHours
FROM ProjectStatus ps
LEFT JOIN ProjectTeam pt ON ps.projectId = pt.projectId
ORDER BY ps.ProjectHealth DESC, ps.endDate;


-- 6. Employee Tenure and Salary Growth Analysis
WITH EmployeeTenure AS (
SELECT empId, name, hireDate,
DATEDIFF(year, hireDate, GETDATE()) as yearsOfService,
DATEDIFF(month, hireDate, GETDATE()) as monthsOfService
FROM EMPLOYEE
),
SalaryHistory AS (
SELECT et.empId, et.name, et.yearsOfService,
s.amount as currentSalary,
s.amount / NULLIF(et.yearsOfService, 0) as avgYearlyIncrease
FROM EmployeeTenure et
JOIN SALARY s ON et.empId = s.empId
)
SELECT name, yearsOfService, currentSalary,
COALESCE(avgYearlyIncrease, currentSalary) as avgYearlyIncrease,
CASE
WHEN yearsOfService < 2 THEN 'New Employee'
WHEN yearsOfService BETWEEN 2 AND 5 THEN 'Mid-Level'
ELSE 'Senior Employee'
END as TenureCategory
FROM SalaryHistory
ORDER BY yearsOfService DESC;


-- 7. Department Cross-Analysis
WITH DepartmentMetrics AS (
SELECT d.deptId, d.deptName,
COUNT(DISTINCT e.empId) as employeeCount,
COUNT(DISTINCT p.projectId) as projectCount,
COALESCE(SUM(p.budget), 0) as totalProjectBudget,
AVG(s.amount) as avgSalary
FROM DEPARTMENT d
LEFT JOIN EMPLOYEE e ON d.deptId = e.deptId
LEFT JOIN PROJECT p ON d.deptId = p.deptId
LEFT JOIN SALARY s ON e.empId = s.empId
GROUP BY d.deptId, d.deptName
),
DepartmentEfficiency AS (
SELECT deptId,
CASE
WHEN employeeCount > 0 THEN totalProjectBudget / employeeCount
ELSE 0
END as budgetPerEmployee,
CASE
WHEN projectCount > 0 THEN employeeCount * 1.0 / projectCount
ELSE 0
END as employeesPerProject
FROM DepartmentMetrics
)
SELECT dm.deptName,
dm.employeeCount,
dm.projectCount,
dm.totalProjectBudget,
dm.avgSalary,
de.budgetPerEmployee,
de.employeesPerProject
FROM DepartmentMetrics dm
JOIN DepartmentEfficiency de ON dm.deptId = de.deptId
ORDER BY dm.totalProjectBudget DESC;


-- 8. Performance Review Insights
WITH ReviewStats AS (
SELECT e.empId, e.name, e.deptId,
COUNT(pr.reviewId) as reviewCount,
AVG(pr.rating) as avgRating,
MIN(pr.rating) as minRating,
MAX(pr.rating) as maxRating
FROM EMPLOYEE e
LEFT JOIN PERFORMANCE_REVIEW pr ON e.empId = pr.empId
GROUP BY e.empId, e.name, e.deptId
),
DeptAvgRating AS (
SELECT deptId,
AVG(avgRating) as deptAvgRating
FROM ReviewStats
WHERE avgRating IS NOT NULL
GROUP BY deptId
)
SELECT rs.name,
d.deptName,
rs.reviewCount,
rs.avgRating,
dar.deptAvgRating,
CASE
WHEN rs.avgRating > dar.deptAvgRating THEN 'Above Department Average'
WHEN rs.avgRating = dar.deptAvgRating THEN 'At Department Average'
WHEN rs.avgRating < dar.deptAvgRating THEN 'Below Department Average'
ELSE 'No Reviews'
END as PerformanceLevel
FROM ReviewStats rs
JOIN DEPARTMENT d ON rs.deptId = d.deptId
LEFT JOIN DeptAvgRating dar ON rs.deptId = dar.deptId
ORDER BY CASE WHEN rs.avgRating IS NULL THEN 1 ELSE 0 END, rs.avgRating DESC;


-- 9. Attendance Pattern Analysis
WITH AttendanceStats AS (
SELECT empId,
COUNT(*) as daysPresent,
AVG(DATEDIFF(hour, timeIn, timeOut)) as avgHoursWorked,
MIN(timeIn) as earliestArrival,
MAX(timeOut) as latestDeparture
FROM ATTENDANCE
WHERE workDate >= DATEADD(month, -1, GETDATE())
GROUP BY empId
),
EmployeeAttendance AS (
SELECT e.empId, e.name, d.deptName,
COALESCE(a.daysPresent, 0) as daysPresent,
COALESCE(a.avgHoursWorked, 0) as avgHoursWorked,
a.earliestArrival,
a.latestDeparture
FROM EMPLOYEE e
JOIN DEPARTMENT d ON e.deptId = d.deptId
LEFT JOIN AttendanceStats a ON e.empId = a.empId
)
SELECT name, deptName, daysPresent, avgHoursWorked,
FORMAT(earliestArrival, 'HH:mm') as earliestArrival,
FORMAT(latestDeparture, 'HH:mm') as latestDeparture,
CASE
WHEN avgHoursWorked >= 9 THEN 'Overtime Worker'
WHEN avgHoursWorked BETWEEN 7.5 AND 9 THEN 'Regular Hours'
WHEN avgHoursWorked > 0 THEN 'Part Time'
ELSE 'No Recent Attendance'
END as WorkPattern
FROM EmployeeAttendance
ORDER BY avgHoursWorked DESC;


-- 10. Comprehensive Employee Dashboard
WITH EmployeeSummary AS (
SELECT e.empId, e.name, e.jobTitle, d.deptName,
s.amount as salary,
DATEDIFF(year, e.hireDate, GETDATE()) as yearsOfService
FROM EMPLOYEE e
JOIN DEPARTMENT d ON e.deptId = d.deptId
LEFT JOIN SALARY s ON e.empId = s.empId
),
ProjectSummary AS (
SELECT pa.empId,
COUNT(DISTINCT pa.projectId) as activeProjects,
SUM(pa.hoursAllocated) as totalHours
FROM PROJECT_ASSIGNMENT pa
JOIN PROJECT p ON pa.projectId = p.projectId
WHERE p.status = 'In Progress'
GROUP BY pa.empId
),
ReviewSummary AS (
SELECT empId,
AVG(rating) as avgRating,
MAX(reviewDate) as lastReviewDate
FROM PERFORMANCE_REVIEW
GROUP BY empId
)
SELECT es.name,
es.jobTitle,
es.deptName,
es.salary,
es.yearsOfService,
COALESCE(ps.activeProjects, 0) as activeProjects,
COALESCE(ps.totalHours, 0) as projectHours,
rs.avgRating,
rs.lastReviewDate,
CASE
WHEN rs.lastReviewDate < DATEADD(year, -1, GETDATE()) OR rs.lastReviewDate IS NULL
THEN 'Review Overdue'
ELSE 'Review Current'
END as reviewStatus
FROM EmployeeSummary es
LEFT JOIN ProjectSummary ps ON es.empId = ps.empId
LEFT JOIN ReviewSummary rs ON es.empId = rs.empId
ORDER BY es.name;