fix transaction Nan

src/services/postgres/ProductsService.js

@@ -28,7 +28,7 @@ class ProductsService {
     const query = {
       text: `SELECT 
               products.id, products.name, products.description, price, cost
-              ${withStock === 'true' ? ', stock' : ''}
+              ${withStock === 'true' ? ', stock, sale, purchase' : ''}
               ${withCategory === 'true' ? ', categories.name as category_name' : ''}
             FROM products
             ${withStock === 'true' ? 'LEFT JOIN stocks ON stocks.product_id = products.id' : ''}

src/services/postgres/PurchasesService.js

@@ -28,7 +28,8 @@ class PurchasesService {
       const purchaseId = purchase.rows[0].id;
 
       await items.map(async (item) => {
-        await client.query(`UPDATE stocks SET stock = '${+item.stock + +item.quantity}', purchase = '${+item.purchase + +item.quantity}' WHERE product_id = '${item.productId}'`);
+        const { rows } = await client.query(`SELECT stock, purchase FROM stocks WHERE product_id = '${item.productId}'`)
+        await client.query(`UPDATE stocks SET stock = '${+rows[0].stock + +item.quantity}', purchase = '${+rows[0].purchase + +item.quantity}' WHERE product_id = '${item.productId}'`);
 
         const itemQuery = {
           text: `INSERT INTO purchase_items(purchase_id, product_id, quantity, cost) VALUES ('${purchaseId}', '${item.productId}', '${item.quantity}', '${item.cost}')`,