From d92b491865e84086c1241c98ceb69373330b04ba Mon Sep 17 00:00:00 2001
From: yikth <netyth@gmail.com>
Date: Fri, 4 Sep 2020 20:59:14 +0800
Subject: [PATCH] prepare homework1

---
 README.md                                     |  53 +++++-
 .../homework1/backend_database_homework1.docx | Bin 0 -> 16296 bytes
 files/sample-homework-data.sql                | 173 ++++++++++++++++++
 3 files changed, 221 insertions(+), 5 deletions(-)
 create mode 100644 files/homework1/backend_database_homework1.docx
 create mode 100644 files/sample-homework-data.sql

diff --git a/README.md b/README.md
index 33d6148..14b7d0e 100644
--- a/README.md
+++ b/README.md
@@ -295,7 +295,9 @@ mysql> ALTER TABLE table2
        ADD FOREIGN KEY (COL2) REFERENCE table1(COL2);
 ```
 
-* Practical Exercise #4
+## Practical Exercise #4 
+
+### Trial Result
 
 ```sql
 // Q1
@@ -317,7 +319,48 @@ mysql> select s.seller_id, s.seller_name, avg(t.transaction_amount) FROM seller
 
 ```
 
-PE #4 Answers
-1. select c.customer_name, t.transaction_datetime from customer as c left join transaction as t on c.customer_id = t.customer_id;
-2. select c.customer_name, max(t.transaction_datetime) from customer as c left join transaction as t on c.customer_id = t.customer_id group by c.customer_id;
-3. select s.seller_name, avg(t.transaction_amount) from seller as s left join transaction as t on s.seller_id = t.seller_id group by s.seller_id;
+### Model Answers
+
+```sql
+// Q1
+mysql> select c.customer_name, t.transaction_datetime from customer as c left join transaction as t on c.customer_id = t.customer_id;
+
+
+// Q2
+mysql> select c.customer_name, max(t.transaction_datetime) from customer as c left join transaction as t on c.customer_id = t.customer_id group by c.customer_id;
+
+
+// Q3
+mysql> select s.seller_name, avg(t.transaction_amount) from seller as s left join transaction as t on s.seller_id = t.seller_id group by s.seller_id;
+```
+
+## Data mock tools
+* [mockaroo](https://www.mockaroo.com/)
+* [generatedata](https://www.generatedata.com/)
+
+## Using MySQL Shell
+1. Switch to SQL mode
+```sql
+MySQL JS> \sql
+
+// connect data
+MySQL JS> \connect root@localhost:3306
+
+// proceed with normal sql command
+MySQL localhost:3306 ssl SQL> show databases;
+
+// open ntuc db
+MySQL localhost:3306 ssl SQL> use ntuc;
+
+// show tables in ntuc
+MySQL localhost:3306 ssl SQL> show tables;
+
+// show store_test table description
+MySQL localhost:3306 ssl SQL> describe store_test;
+
+// display table records
+MySQL localhost:3306 ssl SQL> select * from store_test;
+
+
+
+```
\ No newline at end of file
diff --git a/files/homework1/backend_database_homework1.docx b/files/homework1/backend_database_homework1.docx
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diff --git a/files/sample-homework-data.sql b/files/sample-homework-data.sql
new file mode 100644
index 0000000..7f91ff5
--- /dev/null
+++ b/files/sample-homework-data.sql
@@ -0,0 +1,173 @@
+-- MySQL dump 10.13  Distrib 8.0.19, for osx10.15 (x86_64)
+--
+-- Host: 127.0.0.1    Database: test
+-- ------------------------------------------------------
+-- Server version	8.0.19
+
+/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
+/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
+/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
+/*!50503 SET NAMES utf8mb4 */;
+/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
+/*!40103 SET TIME_ZONE='+00:00' */;
+/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
+/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
+/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
+/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
+
+--
+-- Table structure for table `customer`
+--
+
+DROP TABLE IF EXISTS `customer`;
+/*!40101 SET @saved_cs_client     = @@character_set_client */;
+/*!50503 SET character_set_client = utf8mb4 */;
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+  `customer_email` varchar(255) DEFAULT NULL,
+  `customer_wallet` double(11,0) NOT NULL,
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+CREATE TABLE `seller` (
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+/*!50503 SET character_set_client = utf8mb4 */;
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+  `product_id` int NOT NULL,
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+  `seller_id` int NOT NULL,
+  `customer_id` int NOT NULL,
+  `product_id` int NOT NULL,
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+  KEY `customer_id` (`customer_id`),
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