Post on 17-Dec-2015
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SQL - Select
• Join / Outer Join
• Sub queries
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1. Join
• Join
• Outer join
• Left outer join
• Right outer join
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1.1 Join
• List customer ACME’s orders record in January
• Select * from customers where cname = ‘ACME’• Select * from orders where cid = ‘c001’ and month = ‘jan’
• select o.* from customers c, orders o where c.cid = o.cid and cname = 'ACME' and month = 'jan'
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1.1 Join (cont)
• List the names of all customers who have bought comb
• Select pid from products where pname = ‘comb’• Select cid from orders where pid = ‘p01’• Select cname from customers where cid = ….
• Select cname from customers c, orders o, products p where p.pid = o.pid and c.cid = o.cid and p.pname = ‘comb’
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1.1 Join (cont)
• List the names of all customers who have bought comb
• Select distinct cname from customers c, orders o, products p where p.pid = o.pid and c.cid = o.cid and p.pname = 'comb'
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1.1 Join (cont)
• List all customer pairs who live in the same city
• Select c1.cid, c2.cid from customers c1, customers c2 where c1.city = c2.city and c1.cid != c2.cid
• Select c1.cid, c2.cid from customers c1, customers c2 where c1.city = c2.city and c1.cid < c2.cid
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1.1 Join (cont)
• List all the product names that have been ordered by at least two customers.
• select distinct p.pname, o1.pid from orders o1, orders o2, products p where o1.pid = p.pid and o1.pid = o2.pid and o1.cid < o2.cid
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1.1 Join (cont)
• List the agent names and their total sale amount (orders.dollars).
• select aname, sum(dollars) total_sales from agents a, orders o where a.aid = o.aid group by a.aid, a.aname
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1.2 Outer join
A B1 B2
a1 b1 b1
R lxl S
C
c1
a1 b1 b1 c2
a2 b1 b2 c3
A B1 B2
a1 b1 b1
a1 b2 b1
a2 b1 b2
B1 B2 C
b1 b1 c1
b1 b1 c2
b1 b2 c3
b2 b2 c4
R
S
A B1 B2
a1 b1 b1
R lxlo S
C
c1
a1 b1 b1 c2
a2 b1 b2 c3
a1 b2 b1 null
null b2 b2 c4
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1.2 Outer Join (cont)• Modification to CAPS database.• 1. Add two more records• insert agents values ('a07', 'Tony', 'Boston', 8);• insert orders values (1030, 'mar', 'c006', 'a08', 'p01', 800, 400.00);
• 2. Create a new table “Sales”• create table Sales• (aid char(3) not null,• total money• );
• 3. Load data into table “Sales”• Insert into Sales• select aid, sum(dollars) from orders group by aid
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1.2 Outer Join (cont)
Join (inner join)
• select aname, aid, total from sales s join agents a on s.aid = a.aid
• Select aname, a.aid, total from sales s join agents a on s.aid = a.aid
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1.2 Outer Join (cont)
Outer Join
• select aname, a.aid, total from sales s full outer join agents a on s.aid = a.aid
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1.3 Left outer join
A B1 B2
a1 b1 b1
a1 b2 b1
a2 b1 b2
B1 B2 C
b1 b1 c1
b1 b1 c2
b1 b2 c3
b2 b2 c4
R
S
A B1 B2
a1 b1 b1
R left outer join S
C
c1
a1 b1 b1 c2
a2 b1 b2 c3
a1 b2 b1 null
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1.3 Left outer Join (cont)
Left outer Join:
List name, aid and total sale record of agents who have sale records in the sales table.
• select aname, a.aid, total from sales s left outer join agents a on s.aid = a.aid
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1.4 Right outer join
A B1 B2
a1 b1 b1
a1 b2 b1
a2 b1 b2
B1 B2 C
b1 b1 c1
b1 b1 c2
b1 b2 c3
b2 b2 c4
R
S
A B1 B2
a1 b1 b1
R right outer join S
C
c1
a1 b1 b1 c2
a2 b1 b2 c3
null b2 b2 c4
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1.4 Right outer Join (cont)
Right outer Join:
List name, aid and total sale record of agents who have records in the agents table.
• select aname, a.aid, total from sales s left outer join agents a on s.aid = a.aid
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2.1 Sub queries
• List cid values of customers who place orders with agent in Dallas
• Select aid from agents where city = 'Dallas‘
• Select distinct cid from orders where aid in (select aid from agents where city = 'Dallas')
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2.1 Sub queries (cont)
• List the names and discounts of all customers who place order through agents in Dallas
• Select aid from agents where city = 'Dallas‘
• Select distinct cid from orders where aid in (select aid from agents where city = 'Dallas')
• Select cname, discount from customers where cid in (select distinct cid from orders where aid in (select aid from agents where city = 'Dallas'))
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2.1 Sub queries (cont)• List the names of customers who order product
p05.
• Select distinct cname from customers where cid in (select distinct cid from orders where pid = 'p05')
• Select distinct cname from customers where 'p05' in (select pid from orders where cid = customers.cid)
Uncorrelated subquery
Correlated subquery
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2.1 Sub queries (cont)• List the names of customers who do not
order product p05.
• Select distinct cname from customers where cid in (select distinct cid from orders where pid != 'p05')
• Select distinct cname from customers where cid not in (select distinct cid from orders where pid = 'p05')
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2.2 Sub queries – other key words
• Some\ any \ all
• Exists
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2.2 Sub queries – other key words (cont)
• Find agents (aid) with a minimum commission.
• Select aid from agents where percentage <= all (select percentage from agents)
• Select aid from agents where percentage = (select min(percentage) from agents)
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2.2 Sub queries – other key words (cont)
• Find agents (aid) with a minimum commission.
• Select aid from agents where percentage <= any (select percentage from agents)
• Select aid from agents where percentage <= some (select percentage from agents)
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2.2 Sub queries – other key words (cont)
• Find all customers (cid and cname) who have the same discount as that of any of the customers in Dallas
• Select cid, cname from customers where discnt = some (select discnt from customers where city = 'Dallas')
• Select cid, cname from customers where discnt = any (select discnt from customers where city = 'Dallas')
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2.2 Sub queries – other key words (cont)• Find all customer names where the customers places an order
through agent a05
• Select distinct cname from customers where cid in (select cid from orders where aid = 'a05')
• Select distinct c.cname from customers c, orders o where c.cid = o.cid and o.aid = 'a05'
• Select distinct c.cname from customers c where exists (select * from orders o where c.cid = o.cid and o.aid = 'a05')
• Select distinct c.cname from customers c join orders o on c.cid = o.cid and o.aid = 'a05'