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SQL – Part II
Yong Choi
School of Business
CSU, Bakersfield
SQL Examples – Aggregate Functions
• Example 18: Save as example 18
– How many parts (count number of records) are
in item class HW?
– Use of “count” command
– Count all records: count(*)
– No idea? Try to figure out manually!
Example 18
SQL Query to Count Records
Example 18
SELECT count(*)
FROM Part
WHERE Class=________;
SQL Examples – Aggregate Functions
• Example 19: Save as example 19
– Find the number of customers and the total of
their balances.
– Calculate total: sum(field name)
Example 19
SQL Query to Count Records and
Calculate a Total
Example 19
SELECT count(*), Sum(________)
FROM Customer;
SQL Examples – Aggregate Functions
• Example 20: Save as example 20
– Find the total number of customers and the total
of their balances. Change the column names for
the number of customers and the total of their
balances to CustomerCount and
BalancesTotal.
– Assign column name using “AS” command
Example 20
SQL Query to Perform Calculations and
Rename Fields
Example 20
SELECT count(*) AS CustomerCount,
Sum(Balance) AS _____________
FROM Customer;
SQL Examples – Nested Query
• A query inside another query
– A inside query (sub-query) is evaluated first. It is common to
enclose sub-query in parentheses for readability!!
• Example 21: Save as example 21
– List the order number for each order from the order
line table for a part located in warehouse 3. That
is, we are looking for list of OrderNum that is
associated with warehouse 3.
– No idea? Try to figure out manually!
Example 21
SQL Query with Subquery
Example 21
SELECT OrderNum
FROM OrderLine
WHERE PartNum IN
(SELECT __________
FROM _______
WHERE ___________);
SQL Examples - Grouping
• Use GROUP BY clause
– ONLY grouping, NOT sorting (usually associated
with ORDER BY clause)
• Example 22: Save as example 22
– For each sales rep, list the rep number, the
number of customers assigned to each rep, and
the average balance of the rep’s customers.
– Rename the count of the number of customers
and the average of the balances to
NumOfCustomers and AverageBalance
Example 22
SQL Query to Group Records
# of customers are grouped by each sales rep #
Example 22
SELECT RepNum,
Count(*) AS NumOfCustomer,
Avg(Balance) AS AvgBalance
FROM Customer
GROUP BY __________
SQL Examples – Grouping (con’t)
• Example 23: Save as example 23
– For each sales rep with fewer than four customers, list
the rep number, the number of customers assigned to
the rep, and the average balance of the rep’s
customers. Rename the count of the number of
customers and the average of the balances to
NumOfCustomers and AverageBalance.
– Use of “Having” command.
– Count, Rep. with < 4 customers (group)
Example 23
SQL Query to Restrict Groups
1) # of customers are grouped by each sales rep #
2) Apply the condition to the group
Example 23
SELECT RepNum,
count(*) AS NumCustomer,
Avg(Balance) AS AverageBalance
FROM Customer
GROUP BY RepNum
HAVING ___________;
SQL Examples – Grouping (con’t)
• Use of Where and Having clauses together
– “Where” command must be stated first
• Example 23-1: Save as example 23-1
– Exactly same as example 23. Except, only groups
with fewer than three records and customers with
credit limit of less than $10,000 must be included.
Example 23-1
SQL Query with ‘WHERE’
and ‘HAVING’ Clauses
Example 23-1
SELECT RepNum, count(*) AS NumCustomer,
Avg(Balance) AS AverageBalance
FROM Customer
____________________
GROUP BY RepNum
HAVING Count(*)<3;
Processing Multiple Tables
• Type of Joins (driven from Set Theory)
– Equi-join
– Natural join
– Outer join: Left or Right
– Union join
– Self join
• Each example in the textbook chapter 7
23
Example visualization of different join types with results
returned in shaded area
24
Figure 7-1 Pine Valley Furniture Company Customer and Order
tables with pointers from customers to their orders
These tables are used in queries that follow
Equi-Join Example
• For each customer who placed an order, what is
the customer’s name and order number?
The best way to find out
match customers with their
orders is Including
CustumerID from both tables
26
SQL Examples – Joining Tables
• Example 24: Save as example 24
– List the number and name of each customer
together with the number, last name, and first
name of the sales rep who represents the
customer. If a customer does not have a Rep.,
then he/she must not be included.
– That is, look for matching RepNum from both
tables
Example 24
SQL Query to Join Tables
Example 24
SELECT CustomerNum, CustomerName,
Rep.RepNum, LastName, FirstName
FROM Customer, Rep
WHERE Rep.RepNum=Customer.RepNum;
SQL Examples – Joining Tables (con’t)
• Use of multiple tables with a compound
condition
• Example 25: Save as example 25
– List the number and name of each customer
whose credit limit is $10,000 together with
number, last name, and first name of the sales rep
who represents the customer.
Example 25
Query to Restrict Records in Join
Example 25
SELECT CustomerNum, CustomerName, Rep.RepNum,
LastName, FirstName
FROM Customer, Rep
WHERE Rep.RepNum=____________________
AND CreditLimit=10000;
SQL Examples – Joining Tables (con’t)
• Example 26: Save as example
– For every order, list the order number, order date,
customer number, and customer name. In
addition, for each order line within the order, list
the part number, description, number ordered, and
quoted price. Make sure that everything is
matched. In other words, any “unmatched” records
must not be included.
Example 26
Query to Join Multiple Tables
Example 26
SELECT Orders.OrderNum, Orderdate,
Customer.CustomerNum, CustomerName,
Part.PartNum, Description, NumOrdered, QuotedPrice
FROM Orders, Customer, OrderLine, Part
WHERE Customer.CustomerNum=____________
AND Orders.OrderNum=__________________
AND OrderLine.PartNum=_________________;
SQL Examples – Union
• The union of two tables is a table containing all rows that are in
either the first table, the second table, or both tables.
– Two tables involved in union must have same structure.
• Example 27: Save as example 27
– List the number and name of all customers that
are either represented by sales rep 35 OR that
currently have orders on file, OR both.
– Any “unmatched” records must not be
included.
Example 27 SQL Query to Perform Union
Red: Currently have orders on file
Blue: Represented by sales rep 35
Green: Both
Example 27
SELECT CustomerNum, CustomerName
FROM Customer
WHERE RepNum='35'
UNION
SELECT Customer.CustomerNum, CustomerName
FROM Customer, Orders
WHERE
Customer.CustomerNum=Orders.CustomerNum;
Three Basic Functions by SQL
And Their Basic SQL Commands
1.Data definition (last topic) through the use of
CREATE
2.Data manipulation (next topic) through INSERT,
UPDATE, and DELETE
3.Data querying (we are done with this) through
the use of SELECT AND MANY OTHERS, which is the
basis for all SQL queries.
SQL - Data Manipulation
• Possible with Access
– UPDATE
– INSERT
– DELETE
• Only possible with enterprise level DBMS
– COMMIT
– ROLLBACK
SQL - Data Manipulation (con’t)
• UPDATE command makes data entry corrections
UPDATE Project
SET PrjtLocat = 'Bellaire', DeptNum = 5
WHERE PrjtNum = 10;
UPDATE Employee
SET Salary = Salary * 1.1
WHERE Branch = 'Lincoln';
SQL - Data Manipulation (con’t)
• INSERT command add new data to a table
INSERT INTO Employee (SSN, LastName, FirstName)
VALUES ('Richard', 'Marini', '43433');
• DELETE command removes table row
– DELETE FROM Employee
– WHERE LastName = 'Brown';
SQL - Data Manipulation (con’t)
• COMMIT command store data on the secondary
memory permanently
• ROLLBACK command restores database back to
previous condition if COMMIT hasn’t been used
SQL Examples - Data Manipulation
• Example 28: Save as example 28
– Update the street address of customer 524 to
1445 Rivard
– First, review the current street address of
customer 524 (838 Ridgeland)
Example 28
UPDATE Customer
SET Street = '1445 Rivard'
WHERE CustomerNum='524';
SQL Examples - Data Manipulation
• Example 29: Save as example 29
– Add a new sales rep to the Rep table. Her number
is 16, her name is Sharon Rands, and her address
is 826 Raymond, Altonville, FL 32543. She has
not yet earned any commission, but her
commission rate is 5%(0.05).
– First, review the “Rep” table
Example 29
INSERT INTO Rep
VALUES ('16', 'Rands', 'Shron', '826 Raymond',
'Altonville', 'FL', '32543', 0, 0.05);
SQL Examples - Data Manipulation
• Example 30: Save as example 30
– Delete any row in the Orderline table in which the
part number is BV06
– First, review the part number BV06
(OrderNum21617)
Example 30
DELETE *
FROM OrderLine
WHERE PartNum='BV06';
SQL Examples – Creating a New Table
Using a Existing Table
• Example 31: save as example 31
– Create a new table named SmallCust, consisting
of all fields from the Customer table and those
rows in which the credit limit is less than or equal
to $7,500.
SELECT
INTO Name of table to create
FROM
WHERE
Example 31
SQL Query to Create New Table
Example 31
SELECT * INTO SmallCust
FROM Customer
WHERE CreditLimit<=7500;
SQL - Data Definition I
• Create a database structure to hold all the database
tables; MS Access ONLY can create tables
• Usually, only a DBA can create a new database
structure
SQL syntax for creating a database structure:
CREATE SCHEMA AUTHORIZATION <creator>;
Example:
CREATE SCHEMA AUTHORIZATION JONES;
SQL - Data Definition II
• Specify a new relation by giving it a name and
specifying each of its attributes.
• Each attribute is given a name, a data type to specify
its values, and some constraints on the attribute.
• Syntax:
CREATE TABLE <table name>;
SQL Example – Data Definition
• Example 32: Save as example 32
– Create a table call “CSUB” that contains following
fields:
•
•
•
•
•
•
•
EmpID Number (vs. Number(9) or Num(9))
LastName Char(20)
FirstName Char(20)
Street Char(30)
City Char(20)
State Char(2)
Phone Number
Example 32 (con’t)
Using Access
Create table CSUB
(EmpID Number, LastName Char(20), FirstName Char(20), Street
Char(30), City Char(20), State Char(2), Phone Number);
• Insert following values:
–
–
–
–
–
–
–
EmpID: 123456789
LastName: your lastname
FirstName: your firstname
Street: 9001 Stockdale Hgwy
City: Bakersfield
State: CA
Phone: 6616656691
Example 32
INSERT INTO Employee
VALUES ('987654321', 'Choi', 'Yong', '9001
Stockdale', 'Bakersfield', 'CA', '123456789');
Using Oracle
CREATE TABLE EMPLOYEE
(FNAME
VARCHAR(15)
NOT NULL,
LNAME
VARCHAR(15)
NOT NULL,
SSN
BDATE
CHAR(9)
DATE,
NOT NULL,
SEX
CHAR,
SALARY
DECIMAL(10,2),
SUPERSSN
CHAR(9),
DEPTNO
INT
PRIMARY KEY (SSN),
NOT NULL,
FOREIGN KEY (SUPERSSN) REFERENCES EMPLOYEE(SSN),
FOREIGN KEY (DNO) REFERENCES DEPARTMENT(DNUMBER) );