src/feature/customer/data/repo/customer-db-repo.ts

@@ -46,6 +46,11 @@ export default class CustomerDbRepo implements CustomerRepo {
         }
     }
 
+    async fetchCustomersAmount(): Promise<number> {
+        const data = await sql`SELECT COUNT(*) FROM customers`as postgres.RowList<unknown[]>;
+        return Number(data.count ?? '0');
+    }
+
 
     private customersDto(dbCustomers: customerDbResponse[]): Customer[] {
         return  dbCustomers.map((customer) => this.customerDto(customer));

src/feature/customer/domain/i-repo/customer-repo.ts

@@ -2,6 +2,7 @@ import Customer from "@/feature/customer/domain/entity/customer"
 
 export default interface CustomerRepo {
     fetchList(query: string): Promise<Customer[]>
+    fetchCustomersAmount(): Promise<number>
 }
 
 export const customerRepoKey = "customerRepoKey"

src/feature/customer/domain/usecase/fetch-customers-amount-usecase.ts

@@ -0,0 +1,8 @@
+import serverDi from "@/feature/common/server-di";
+import { customerKey } from "@/feature/customer/customer-key";
+import CustomerRepo, { customerRepoKey } from "@/feature/customer/domain/i-repo/customer-repo";
+
+export default function fetchCustomersAmountUsecase(): Promise<number> {
+    const repo = serverDi(customerKey).resolve<CustomerRepo>(customerRepoKey)
+    return repo.fetchCustomersAmount()
+}