Database on egig.github.io

Some Consideration on Designing Database

Mon, 27 Jan 2020 10:00:00 +0000

My first post this 2020. One of those things I want to write is that what I learn from sharing session from work combined with a few experiences about database MySQL.

There are some that we need to consider when working with database MySQL so our database can work seamlessly effective.

Collation

When creating new database, often ignore about anything else except the short syntax

1CREATE DATABASE <db-name>

Collation is basic thing we should care about. Character set is now evolved, so we need to ready to handle even very strange emoji and smiley in our character set. Without concern about the collation, we likely will get this error

A Way to Do Group By

Mon, 10 Jun 2019 13:00:00 +0000

How do you do Group By in SQL ? (or MySql) ? This post is note about my experience writing query in sql, There is worth-to-note something about ‘Group By’, there is may be better way to do it.

So lets say, we have following schema, table users and table orders, they have relation one to many. One user can has zero or many orders.

 1CREATE TABLE orders
 2(
 3 id INT(11) PRIMARY KEY NOT NULL AUTO_INCREMENT,
 4 title VARCHAR(500) NOT NULL,
 5 order_date DATE NOT NULL,
 6 user_id INT(11) NOT NULL
 7);
 8
 9CREATE TABLE users
10(
11 id INT(10) unsigned PRIMARY KEY NOT NULL AUTO_INCREMENT,
12 name VARCHAR(255) NOT NULL,
13 email VARCHAR(255) NOT NULL,
14);
15
16CREATE UNIQUE INDEX users_email_unique ON users (email);

and suppose we need to get all users for certain order, for SELECT * fan, the query pretty much will looks like this

MongoDB Sort By Nested Array of Object Item

Fri, 29 Mar 2019 21:00:00 +0000

Let’s say, I have this kind of list of Mongodb documents, named hardwares;

 1[
 2	{
 3		_id: ObjectId(...),
 4		name: "Unit x",
 5		parts: [
 6			{ name: "CPU", model: "x" },
 7			{ name: "Memory", size: "4" }
 8		]
 9	},
10	{
11		_id: ObjectId(...),
12		name: "Unit y",
13		parts: [
14			{ name: "CPU", model: "y" },
15			{ name: "Memory", size: "8" }
16		]
17	},
18	{
19		_id: ObjectId(...),
20		name: "Unit z",
21		parts: [
22			{ name: "CPU", model: "z" },
23			{ name: "Memory", size: "2" }
24		]
25	}
26]

Recently I’ve struggle to find a way to sort those document list by nested array of object item, in this case, certain item in parts array.