1. Database Design
Sections 16 & 17 – Columns, Characters, Rows, Concatenations, DISTINCT, DESCRIBE, Logical Operators, Order of Operations, Sorting
9/26/2011

2. Using DESCRIBE (DESC)
Use the DESCRIBE command to display the structure of a table.
DESC[RIBE] tablename;
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3. Describe command
DESCRIBE (DESC) command displays the structure of a table
Try the following: DESC departments;
See the results on the next slide.
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4. Describe command
DESC departments;
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5. Concatenation A concatenation operator:
Concatenation means to connect or link together in a series
Concatenates columns, expressions or character strings to other columns
Is represented by two vertical bars (||) or two “pipes”
Creates a resultant column that is a character expression
“On date, the event was name”
Show students where the pipe (|) character is on their keyboard.
Make up sentences that students must display using the concatenation operator. Demonstrate that leaving a space after or before the single quotation mark also creates a space between words. Point out that an alias will eliminate the SELECT line appearing as the column heading. Run the example twice, the second time with an alias called Event to show the difference.
Using the DJ on Demand EVENT table, create and display :
"On date, the event was name"
Answer:
SELECT 'On ' ||event_date || ' the event was ' ||name
FROM d_events;
SELECT 'On ' ||event_date || ' the event was ' ||name AS Event
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6. Practice SELECT last_name ||', '|| first_name FROM employees;
Using the DJ on Demand EVENT table, create and display : "On date, the event was name”
Run the command again using an alias Events for the column heading
Create SQL to get the phase like “King earns $24000” from the employees table
SELECT doesn’t change data
Note that we have formatted the name to put the last name first and then the first name separated with a comma
SELECT 'On ' ||event_date || ' the event was ' ||name
FROM d_events;
SELECT 'On ' ||event_date || ' the event was ' ||name AS "Events"
FROM d_events
point out “ around an alias, note the column heading is formatted.
SELECT last_name ||' earns ' ||'$'||salary AS "Salary"
FROM employees;
Note: spaces inside the literal ‘ earns ‘
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7. Practice database UCLA
CREATE table UCLA (id number, name varchar2(20));
DESC ucla;
INSERT INTO ucla values(1,'Joe');
values(2,‘Mary');
SELECT * FROM ucla;
We can use the ucla table for practice during lecture
Note name is case sensitive
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8. Using Literal Character Strings
A literal is a character, a number, or a date included in the SELECT list.
Date and character literal values must be enclosed within single quotation marks.
Each character string is output once for each row returned.
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9. Using Literals SELECT id, 'hello’ FROM ucla; hello is a literal
This inserts values in a column of the UCLA table with the value ‘hello’
Try it.
Try this: SELECT id, 15 FROM ucla;
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10. DISTINCT: Eliminating duplicate rows
The default display of queries is all rows, including duplicate rows.
Use the DISTINCT keyword in the SELECT clause to eliminate duplicate rows.
DISTINCT must appear just after the SELECT keyword.
If used with more than one column then every unique combination of these columns will be returned.
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11. DISTINCT practice SELECT job_id FROM employees;
Note the large number of rows returned
Revise using DISTINCT
SELECT DISTINCT job_id FROM employees;
When DISTINCT is after the SELECT it applies to all other fields in the SELECT
SELECT DISTINCT job_id, salary FROM employees;
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12. Limiting rows
SELECT*|{[DISTINCT] column|expression [alias],...} FROM table [WHERE condition(s)];
WHERE clause limits the number of rows.
Example: SELECT DISTINCT year AS “Year” FROM d_cds WHERE year <= 2000;
Run command.
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13. Practice
Each statement below has errors. Correct the errors and execute the query in APEX
SELECT first name FROM f_staffs;
SELECT first_name |"  " | last_name AS “DJs on Demand Clients” FROM d_clients;
SELECT DISCTINCT f_order_lines FROM quantity;
SELECT order number FROM f_orders;
2. a. Missing underscore first_name
b. Incorrect single bar concatenation operator and double quotation marks
c. DISTINCT incorrectly spelled and column and table names in wrong place
d. Missing underscore order_number
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14. Practice Which of the following is TRUE about the following query?
SELECT first_name, DISTINCT birthdate FROM f_staffs;
Only two rows will be returned.
Four rows will be returned.
Only Fred 05-JAN-88 and Lizzie 10-NOV-87 will be returned.
No rows will be returned.
d. No rows will be returned. DISTINCT must appear directly after SELECT.
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15. More Practice
True/False -- The following SELECT statement executes successfully: SELECT last_name, job_id, salary AS Sal FROM employees;
True/False -- The following SELECT statement executes successfully: SELECT * FROM job_grades;
There are four coding errors in this statement. Can you identify them? SELECT employee_id, last_name sal x 12 ANNUAL SALARY FROM employees;
In the arithmetic expression salary* , which operation will be evaluated first?
Answers:
1. True
2. True
3. Missing comma after last_name, sal*12 and "ANNUAL SALARY", sal should be salary
4. salary*12
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16. Practice
Which of the following can be used in the SELECT statement to return all columns of data in the Global Fast Foods f_staffs table?
column names *
DISTINCT id
both a and b
Using SQL to choose the columns in a table uses which capability?
selection
projection
partitioning
join
SELECT department_id, first_name, last_name AS "Employee". The column heading in the query result will appear as:
EMPLOYEE
employee
Employee
"Employee:
Answers:
1. d. both a and b
2. b. projection
3. c. Employee
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17. More Practice
Which statement below will return a list of employees in the following format?
Mr./Ms. Steven King is an employee of our company.
SELECT "Mr./Ms."||first_name||' '||last_name 'is an employee of our company.' AS "Employees“ FROM employees;
SELECT 'Mr./Ms. 'first_name,last_name ||' '||'is an employee of our company.' FROM employees;
SELECT 'Mr./Ms. '||first_name||' '||last_name ||' '||'is an employee of our company.' AS "Employees“ FROM employees
SELECT Mr./Ms. ||first_name||' '||last_name ||' '||"is an employee of our company." AS "Employees“ FROM employees
Which expression below will produce the largest value?
SELECT salary*
SELECT salary* ( )
SELECT 6(salary+ 100)
SELECT salary+6*100
4. c. SELECT 'Mr./Ms. '||first_name||' '||last_name ||' '||'is an employee of our company.' AS "Employees" FROM employees
5. b. SELECT salary* ( )
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18. More Practice
Which is true about SQL statements?
SQL statements are case-sensitive
SQL clauses should not be written on separate lines.
Keywords cannot be abbreviated or split across lines.
SQL keywords are typically entered in lowercase; all other words in uppercase.
Which query will return three columns each with UPPERCASE column headings?
SELECT "Department_id", "Last_name", "First_name“ FROM employees;
SELECT DEPARTMENT_ID, LAST_NAME, FIRST_NAME FROM employees;
SELECT department_id, last_name, first_name AS UPPER CASE FROM employees;
SELECT department_id, last_name, first_name FROM employees;
Answers:
6. c. Keywords cannot be abbreviated or split across lines.
7. b. SELECT DEPARTMENT_ID, LAST_NAME, FIRST_NAME FROM employees;
     d. SELECT department_id, last_name, first_name FROM employees;
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19. More Practice Which statement below will likely fail?
SELCT * FROM employees;
Select * FROM employees;
SELECT * FROM EMPLOYEES;
SelecT* FROM employees;
12. a. SELCT * FROM employees;
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20. Limiting Rows with WHERE
The WHERE clause can compare values in columns, literal values, arithmetic expressions, or functions. It consists of three elements:
Column name
Comparison condition
Expressions, constant, or list of values
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21. WHERE clause
The WHERE clause follows the FROM clause in a SQL statement.
An alias cannot be used in the WHERE clause!
Example:
SELECT last_name, first_name, department_id FROM employees WHERE department_id = 50;
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22. Comparison Operators Operator Meaning = > >= < <= <>
The symbols != and ^= can also represent the not equal to condition.
Operator
Meaning =
Equal to
>
Greater than
>=
Greater than or equal to
<
Less than
<=
Less than or equal to
<>
Not equal to
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23. WHERE clauses Using comparison operators
SELECT last_name,first_name,department_id FROM employees WHERE department_id >= 60;
SELECT last_name,first_name,department_id FROM employees WHERE department_id <> 60;
Write a SELECT statement to produce the following results: The song title is “Meet Me At the Altar.” Where ‘Meet Me At the Altar’ is the title of a song. Remember Oracle SQL is case sensitive
SELECT 'The song title is " ' || title ||‘ .“ ‘
FROM d_songs
WHERE id = 48;
SELECT 'The song title is " ' || title ||' ." '
WHERE title = 'Meet Me At the Altar';
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24. Other comparison operators
BETWEEN …. AND IN
LIKE
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25. BETWEEN ... AND
BETWEEN...AND operator is used to select and display rows based on a range of values.
BETWEEN ... AND are inclusive
SELECT last_name,first_name,department_id FROM employees WHERE department_id BETWEEN 60 AND 90;
SELECT last_name,first_name,department_id FROM employees WHERE department_id NOT BETWEEN 60 AND 90;
SELECT title, year FROM   d_cds WHERE  year  BETWEEN '1999' AND '2001';
For BETWEEN 60 AND 90
Inclusive means that the 60 and 90 are included.
Returns values within the stated range included the stated range values
Lowest value MUST be stated first!
example point out
Note that the year column is defined as a VARCHAR2 datatype. Because of this , the SQL statement could have been written without quotes around the year values:
SELECT title, year
FROM d_cds
WHERE year BETWEEN 1999 AND 2001;
The reason for this is because when Oracle compares a numeric literal (i.e., 1999) against a VARCHAR2 column, Oracle implicitly converts the data into a character (VARCHAR2) datatype.
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26. More Complex WHERE clause
Example:
"I would like to know Global Fast Foods employees whose manager ID is 19 and earn a salary less than $12.00 per hour.
SELECT * FROM f_staffs WHERE manager_id = 19 and salary <12.00;
BETWEEN… AND can be written using normal comparison operators. For example
WHERE year >= ‘1999’ AND year >= ‘2001’; Note field name is repeated for each comparison while not in BETWEEN…AND statement.
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27. WHERE clause using LIKE
LIKE condition allows you to select rows that match either literal characters or number patterns.
% and underscore (_ )
are wildcard characters, used to construct a search string.
% symbol used to represent any sequence of zero or more characters.
Underscore (_ ) symbol used to represent a single character.
Often called a ‘membership condition’
SELECT last_name, first_name
FROM employees
WHERE last_name LIKE '_o%';
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28. LIKE examples
SELECT last_name,first_name,department_id FROM employees WHERE last_name LIKE 'A%';
SELECT last_name,first_name,department_id FROM employees WHERE last_name LIKE '%s’;
SELECT last_name,first_name,department_id FROM employees WHERE last_name LIKE '%s%’;
SELECT last_name,first_name,department_id FROM employees WHERE last_name LIKE ‘_ _ _ _ _s%’; Using 5 underscores
% is used for any sequence of zero or more characters
Underscore _ is used to represent a single character
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29. Like
For an exact match where _ or % are part of the string and not a wildcard use the \ symbol
Select job_id, first_name, last_name
FROM employees
Where job_id LIKE 'SA%';
If cd’s were stored using the following format TRA_6 then the following where be the where clause
WHERE track LIKE ‘TRA\_%’;
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30. Using IS NULL, IS NOT NULL
NULL is unavailable, unassigned, unknown, or inapplicable. No presence of data.
NOT NULL test for presence of data in column/field.
Examples:
SELECT last_name,first_name,department_id, commission_pct FROM employees WHERE commission_pct is NULL;
SELECT last_name,first_name,department_id, commission_pct FROM employees WHERE commission_pct is NOT NULL;
NOTE: you can’t use = you must use is.
Commission_pct = NULL (will not work)
Slide 13: Tell Me / Show Me – IS NULL, IS NOT NULL
Discuss the concept of NULL and the difference between values that are unknown, values that are unknowable, and values that are inapplicable.?
Where does the sky end? Is it unknown, unknowable, or inapplicable?
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31. Practice problems
Display the location type and comments for all DJs on Demand venues that are Private Home.
Who are the partners of DJs on Demand who do not get an authorized expense amount?
2. SELECT  loc_type, comments
FROM d_venues
WHERE loc_type LIKE 'Private Home';
NOTE: limiting field/column is not displayed
5. SELECT  first_name, last_name
FROM d_partners
WHERE auth_expense_amt IS NULL;
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32. IN is like OR’s IN is like a string of OR clauses. Example:
SELECT last_name,first_name,department_id FROM employees WHERE department_id IN(50, 60, 90);
Section 18 In = Include
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33. Logical Comparisons
A logical condition combines the results of two or more conditions to produce a single result. A row is returned ONLY IF the overall result of the condition is true.
AND – Returns TRUE if both conditions are true.
OR – Returns TRUE if either conditions are true.
NOT – Returns TRUE if the condition is false.
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34. Examples of using Logical operators
SELECT id, title, duration, type_code FROM d_songs WHERE id > 40 AND type_code = 77;
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35. Precedence using AND & OR
Evaluate these two examples. What is the difference?
SELECT last_name, job_id, salary FROM employees WHERE job_id = ‘SA_REP’ OR job_id=‘AD_PRES’ AND salary>15000;
SELECT last_name, job_id, salary FROM employees WHERE (job_id = ‘SA_REP’ OR job_id=‘AD_PRES’) AND salary>15000;
AND before OR
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36. Logical Comparisons Logical conditions (a few examples)
SELECT last_name, job_id, department_id FROM employees WHERE job_id = ‘SA_REP’ OR department_id = 10;
SELECT last_name, job_id, SALARY FROM employees WHERE job_id = ‘SA_REP’ AND salary > 15000;
Can you explain what rows are to be returned in each?
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37. Logical operator
Write a select statement to find an address in the DJs on Demand database d_venues table that has the word "Primrose" in the description.
SELECT  address FROM  d_venues WHERE address LIKE '%Primrose%‘;
Variations:
…WHERE id NOT IN(105, 206, 332);
…WHERE id != 105 and id != 206 and id!= 332;
Look at the data in the d_venues table before trying to do this problem.
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38. Examples: Ms. Smith whose employee_id is 50
Below are phrases and conditions in which they would not be true
employee_id = 100 AND last_name LIKE 'S%'  
Ms. Smith whose employee_id is 50
Employee_id 100 whose last name is King
department = 10 AND employee_id  = 100;
Employee_id 100 is in department 20
Employee_id 50 is in department 10
Take each example and find cases in which they would be FALSE. The false choices are listed below the conditions.
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39. Complex AND and OR clause
Take an arc
#id
ID = A
ID = B
Start with the arc condition then look at next slide.
ID = C
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40. Complex AND and OR clause
Example Table: ID A B C PK
Fk1
Fk2
Fk3 * O
This again represents the ARC in a tabular form
See next slide
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41. Complex AND and OR clause
WHERE clause example for ARC:
WHERE ((A is NOT NULL and B is NULL and C is NULL) OR (A is NULL and B is NOT NULL and C is NULL) OR (A is NULL and B is NULL and C is NOT NULL)) /*--- comment ---*/
Precedence is AND before OR
This would be the Compound AND/OR representing the ARC condition
The results would be the same without the () because of precedence.
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42. Rules of Precedence Order Operator 1 2 3 4 5 6 7 8
Arithmetic operations 2
Concatenation operators 3
Comparison conditions 4
IN [NOT] NULL, LIKE, [NOT] IN 5
[NOT] BETWEEN 6
NOT logical operator 7
AND logical operator 8
OR logical operator
The rules of precedence determine the order in which expressions are evaluated and calculated. The table lists the default order, which can be overridden by using parentheses.
KNOW THIS ONE. Might want to print it out to have when coding.
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43. Order of Operations Examples
What order will these process in?
SELECT last_name, specialty, auth_expense_amt FROM   d_partners WHERE  specialty ='All Types‘ OR     specialty IS NULL AND   auth_expense_amt = ;
SELECT last_name, specialty, auth_expense_amt FROM   d_partners WHERE  (specialty ='All Types‘ OR     specialty IS NULL) AND   auth_expense_amt = ;
The order of operations is:
1. Specialty IS NULL AND auth_expense_amt = Both these conditions must be met to be returned.
2. Any instance of specialty = 'All Types' will be returned.
1. The values in the parentheses are selected.
2. All instances of the values in the parentheses that also match auth_expense_amt = will be returned.
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44. Examples &
“I need to know who of the Global Fast Foods employees makes more than $6.50/hour and their position is not Order Taker.“
What's my address? Because I have been working for Oracle since the beginning of 1996, I make more than $9000 per month. Because I make so much money, I don't get a commission.
3. SELECT last_name
FROM f_staffs
WHERE salary > 6.50 AND staff_type != 'Order Taker';
8. SELECT
FROM employees
WHERE  hire_date BETWEEN '01-JAN-96' AND '31-DEC-96' AND salary > 9000 AND commission_pct IS NULL;
MHARTSTE
An alternative solution for #8 is:
SELECT
WHERE  hire_date > '01-JAN-96' AND salary > 9000
AND commission_pct IS NULL;
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45. Examples: AND and OR conditions
What are the titles of the jobs whose minimum salary is 4000 and whose maximum salary is 9000?
Try this with OR and then AND
Rewritten query including the salary columns to verify that both conditions are met:
Note: you might want to review the jobs table fields/columns etc.
1. SELECT job_title,min_salary, max_salary (or just job_title)
FROM jobs
WHERE min_salary = 4000 or max_salary = 9000;
2. SELECT job_title,min_salary, max_salary
WHERE min_salary = 4000 AND max_salary = 9000;
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46. Sorting rows ORDER BY Information sorted by the column referenced.
ORDER BY clause follows the FROM clause and is at the end of the SELECT statement.
ORDER BY clause sorts in ascending order by default.
Only limit to how many columns can be added to the ORDER BY clause is the number of columns in the table.
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47. ORDER BY Example of single value sort
SELECT department_id, job_id, last_name, salary FROM employees ORDER BY department_id desc;
Note: desc was used to denote descending order because ascending is the default.
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48. ORDER BY multiple values
SELECT department_id, job_id, last_name, salary FROM employees ORDER BY department_id, job_id, salary;
SELECT department_id, job_id, last_name, salary FROM employees ORDER BY department_id, job_id desc, salary;
SELECT department_id, job_id, last_name, salary FROM employees ORDER BY 3; The 3 is field from SELECT
SELECT department_id, job_id, last_name, salary FROM employees ORDER BY 2, last_name;
Note sort order for results. Note the use of a number in sort clause which denotes the field in that numeric position of the Select statement.
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49. Sort order The default sort order is ascending.
Numeric values are displayed lowest to highest.
Date values are displayed with the earliest value first.
Character values are displayed in alphabetical order.
Null values are displayed last in ascending order and first in descending order.
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50. ORDER BY multiple values
Place the following hire dates in descending order: 22-MAY-85, null, 10-JAN-04, 17-NOV-55, 21-DEC-98
Write a query to find the answer, using the employees table and hire_date column
Answer: null, 10-JAN-04, 21-DEC-98, 22-MAY-85, 17-NOV-55
SELECT hire_date
FROM employees
ORDER BY hire_date DESC;
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51. Order of execution in a SELECT statement
The order of execution of a SELECT statement is as follows:
FROM clause -- locates the table that contains the data
WHERE clause -- restricts the rows to be returned
SELECT clause -- selects from the reduced data set the columns requested
ORDER BY -- orders the results set
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52. Example
SELECT employee_id, first_name FROM employees WHERE employee_id < 105 ORDER BY last_name;
What order does this execute in?
FROM clause -- locates the table that contains the data
WHERE clause -- restricts the rows to be returned
SELECT clause -- selects from the reduced data set the columns requested
ORDER BY -- orders the results set
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53. &
Create a query that will return all the DJ on Demand CD titles ordered by year with titles in alphabetical order. 2.
SELECT title, year
FROM d_cds
ORDER BY year, title;
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54. Produce the show results
Write a SQL statement using the employees table and the ORDER BY clause that could retrieve the information in the following table. Return only those employees with employee_id<125.
5. SELECT department_id, last_name, manager_id
FROM employees
WHERE employee_id < 125
ORDER BY department_id DESC, last_name DESC;
Discuss the graphics with students. Write SELECT statements for each.
SELECT DISTINCT item_number, item_names ASC
FROM inventory;
SELECT last_name, salary DESC
ORDER BY salary DESC;
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55. Function classification
Single-row and multi-row functions
Single-row functions operate on a single row and return only one result per row.
Multiple-row functions can manipulate groups of rows to give one result per group of rows.
This section provides a brief overview of this topic. It is covered in depth in the next section.
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56. Function types
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57. SQL Single row functions
Character
Converting character values from uppercase to lowercase
Number
rounding off
Manipulate output for groups of rows by finding an average or sum for several rows
Date
Format dates and numbers for display
Conversion
Convert column data types such as converting a character string to a number or date
General
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58. Functions:
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59. Single-row functions
They can be used in SELECT, WHERE, and ORDER BY clauses.
They return ONE result per row.
They can return a data value of a different type.
They can possibly expect one or more arguments or values sent to them.
They act on each row returned in the query.
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60. Examples
SELECT 'The most popular song in our collection is ' || UPPER(title)AS "Most Requested” FROM d_songs WHERE id = 47;
SELECT CONCAT(title, year) FROM d_cds;
1. Most Requested (Column heading from Alias)
The most popular song in our collection is HURRAH FOR TODAY
2. TITLE (column heading uses the first column in Concat.)
The Celebrants Live in Concert1997
Party Music for All Occasions2000
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61. Examples Use ‘ single quote when referring to data in a database
Use “ “ for text as an alias if text has space or specific case etc.
In an ORDER BY clause you can use an alias, expression, number, field names
SELECT department_id, job_id AS job, last_name, salary*12 FROM employees ORDER BY job;
SELECT department_id, job_id AS job, last_name, salary*12 FROM employees ORDER BY salary*12;
SELECT department_id, job_id AS job, last_name, salary*12 FROM employees ORDER BY 3;
Note ORDER BY was by ALIAS
Note ORDER BY is using an expression
3 is third field in select statement
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62. Examples
Fields used in ORDER BY don’t have to be used in SELECT clause
SELECT last_name FROM employees WHERE salary > 4000 ORDER BY job_id;
In development you might want to include the ORDER BY field in SELECT to verify that your getting the correct results, then remove the field.
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63. Single-row function example
The single-row function is done for every row
What would be returned from this statement?
SELECT last_name || ' ' || first_name, salary,round(salary,-3) FROM employees WHERE salary>400;
Round function has two arguments, first the field and 2nd the position to round off to. -3 rounds off to thousands (three to left of decimal)
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64. Multi-Row Functions
Aggregate data
AVG
COUNT
MAX
MIN
SUM
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