# Fix Customer Email Duplicate Error

## Problem
The unique index on `Customers.Email` was enforcing **global uniqueness** (across all companies), but in a multi-tenant system, different companies should be able to have customers with the same email address.

## Solution
Change the unique index to be scoped to `CompanyId`, allowing the same email across different companies while still preventing duplicates within the same company.

---

## Quick Fix (Run SQL Script)

### Step 1: Run the SQL Script
1. Open **SQL Server Management Studio**
2. Connect to your testing server
3. Open the file: **`fix-customer-email-index.sql`**
4. **Execute** the script

This will:
- ✅ Drop the old global unique index
- ✅ Create new company-scoped unique index
- ✅ Show verification that it worked

### Step 2: Test Seeding
1. Go to your web app: `/SeedData`
2. Click **"Seed Company Data"**
3. Should work perfectly now! ✨

---

## Alternative: Use EF Migration (For Production Deployment)

If you want to use EF migrations for a cleaner deployment:

### From Web Project Directory:
```bash
cd src/PowderCoating.Web

# Apply the migration
dotnet ef database update --project ../PowderCoating.Infrastructure
```

This will apply the migration: **`FixCustomerEmailIndexForMultiTenancy`**

---

## What Changed

### Before (Old Index):
```sql
CREATE UNIQUE INDEX IX_Customers_Email ON Customers (Email)
WHERE [Email] IS NOT NULL
```
❌ Problem: Only ONE customer across ALL companies can have `john.smith@acmemfg.com`

### After (New Index):
```sql
CREATE UNIQUE INDEX IX_Customers_Email ON Customers (CompanyId, Email)
WHERE [Email] IS NOT NULL AND [IsDeleted] = 0
```
✅ Solution: EACH company can have a customer with `john.smith@acmemfg.com`

---

## Examples

### Now This Works:
| CompanyId | Email | Status |
|-----------|-------|--------|
| 1 | john.smith@acmemfg.com | ✅ OK |
| 2 | john.smith@acmemfg.com | ✅ OK (different company) |
| 1 | jane.doe@example.com | ✅ OK |

### This Still Prevents Duplicates:
| CompanyId | Email | Status |
|-----------|-------|--------|
| 1 | john.smith@acmemfg.com | ✅ First insert OK |
| 1 | john.smith@acmemfg.com | ❌ DUPLICATE (same company) |

---

## Verification

After running the script, verify the index:

```sql
-- Check the new index definition
SELECT
    i.name AS IndexName,
    i.is_unique AS IsUnique,
    STRING_AGG(COL_NAME(ic.object_id, ic.column_id), ', ') AS IndexColumns,
    i.filter_definition AS Filter
FROM sys.indexes i
INNER JOIN sys.index_columns ic ON i.object_id = ic.object_id AND i.index_id = ic.index_id
WHERE i.object_id = OBJECT_ID('Customers')
    AND i.name = 'IX_Customers_Email'
GROUP BY i.name, i.is_unique, i.filter_definition
```

**Expected Result:**
- IndexName: `IX_Customers_Email`
- IsUnique: `1` (true)
- IndexColumns: `CompanyId, Email`
- Filter: `[Email] IS NOT NULL AND [IsDeleted] = 0`

---

## Build & Deploy

The migration is already in your code:
```
src/PowderCoating.Infrastructure/Migrations/
  └─ 20260211160000_FixCustomerEmailIndexForMultiTenancy.cs
```

When you deploy to production:
```bash
dotnet ef database update --project ../PowderCoating.Infrastructure
```

Will automatically apply this migration.

---

## Summary

✅ **Index Fixed** - Scoped to CompanyId
✅ **Multi-Tenancy Safe** - Same email OK across companies
✅ **Duplicate Prevention** - Still blocks duplicates within a company
✅ **Soft Delete Aware** - Ignores deleted records

You're ready to seed! 🎉