SQL query to relate 2 tables - sqlite

Question

I want to relate following 2 tables in sqlite3. What I understood from other examples is that we should have some common field between each table, so I added order_ID.
1) How to write sqlite queries for creating the relation between these tables?
2) How to manage Table 2, where same order can have multiple products, so order ID is repeated. An order can have min 1 and max 10 products. So it has dynamic range of 1-10.
table 1:
order_ID date buyer ship_chr
001 01/01 abc 15
002 05/01 xyz 10
table 2:
order_ID prod quantity rate
001 pen 50 2
001 paper 25 1
001 pin 50 2
002 paper 25 1
002 pen 100 2

Answer 1

It looks like you want to store orders and information about those orders. First, make an orders table.
create table orders (
id integer primary key autoincrement,
created_at timestamp not null default current_timestamp,
buyer text not null,
ship_chr text not null
)
Note that instead of order_id, the primary key of a table is just id.
It's not required, but it is a convention I like as it keeps primary and foreign keys distinct.
Also note that I'm using the timestamp type to store dates, this will make working with those dates much easier as you can use SQLite date functions.
Now we need a table for information about what is in each order.
create table order_products (
id integer primary key autoincrement,
order_id integer not null references orders(id),
product text not null,
quantity integer not null,
rate integer not null
)
This sets up a one-to-many relationship betweeen orders and order_products.
One order can have many products. You can link these tables together using
a join. Here's how you'd get
the buyer for each product.
select o.buyer, op.product, op.quantity
from order_products op
join orders o on o.id = op.order_id
abc|pen|50
abc|paper|25
abc|pin|50
xyz|paper|25
xyz|pen|100
join orders o on o.id = op.order_id says for every row in order_products find one in orders where order.id matches the row's order_id and treat them both as a single row.
From here you'll probably want to make products and buyer their own tables
as well to store any information about the buyers and products. It also ensures
that the products and buyers exist avoiding typos.
create table buyers (
id integer primary key autoincrement,
name text not null,
address text not null,
phone text not null
);
create table products (
id integer primary key autoincrement,
name text not null,
stock integer not null default 0
);
create table orders (
id integer primary key autoincrement,
created_at timestamp not null default current_timestamp,
buyer_id integer references buyers(id) not null,
ship_chr text not null
);
create table order_products (
id integer primary key autoincrement,
order_id integer not null references orders(id),
product_id integer not null references products(id),
quantity integer not null,
rate integer not null
);
Then you can join everything together to get information about products and buyers.
select b.name, p.name, op.quantity
from order_products op
join orders o on o.id = op.order_id
join buyers b on b.id = o.buyer_id
join products p on p.id = op.product_id
name|name|quantity
abc|pen|50
abc|paper|25
abc|pin|50
xyz|paper|25
xyz|pen|100
SQL Fiddle
If you don't do this now it will be harder to do later.