1. CS122 Using Relational Databases and SQL
12/7/2018
CS122 Using Relational Databases and SQL
6. Functions
Daniel Firpo
Slides prepared by Randy Moss
Department of Computer Science
California State University, Los Angeles

2. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

3. 12/7/2018
Concatenation
Concatenation is the combination of two or more text values into one text value
Can concatenate multiple fields or fields with constant text
6. Functions CS1222_F2018

4. Concatenation Syntax Concat(expression1, expression2,…)
12/7/2018
Concatenation
Syntax
Concat(expression1, expression2,…)
Concatenate a series of text values separated by commas
If any of the arguments is null, the function will return null
Concat_WS(Separator, expression1, expression2,…)
The separator is placed between each of the text values
The function will ignore nulls unless the separator is a null, in which case it returns a null.
6. Functions CS1222_F2018

5. Concatenation Example (1)
12/7/2018
Concatenation Example (1)
List the full name of each member
Select Concat_WS(' ', firstname , lastname)
As fullname
From Members
6. Functions CS1222_F2018

6. Concatenation Example (2)
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Concatenation Example (2)
Report the City, State, and Zip of each member, formatted as City, State Zip.
SELECT Concat(City, ' ' ,Region,' ',
Postalcode) As MailAddr
FROM Members
6. Functions CS1222_F2018

7. Concatenation Example (3)
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Concatenation Example (3)
Report each lead source preceded by the text, 'source: ' along with a count of the number of artists leads from that source.
Select Concat('source: ',Leadsource) As Source, Count(*) As NumLead
From Artists
Group by Source
6. Functions CS1222_F2018

8. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

9. Text Functions in MySQL
12/7/2018
Text Functions in MySQL
LPad(string, num_char, pad_chars) RPad(string,num_char,pad_chars)
Makes a string a certain length (num_char) by adding a certain set of pad characters (pad_chars) to the left (LPad) or right (RPad).
6. Functions CS1222_F2018

10. Examples =10 Length('Larry King') Left('Larry King',5)
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Examples
=10
Length('Larry King')
Left('Larry King',5)
Right('Larry King',4)
Substring('Larry King', 2, 4)
Locate('king', 'Larry King')
LTrim(' Larry ')
RTrim(' Larry ')
Trim(' Larry ')
Upper('Larry')
Lower('Larry')
='Larry'
='King'
= 'arry'
= 7
= 'Larry '
=' Larry'
= 'Larry'
= 'LARRY'
= 'larry'
6. Functions CS1222_F2018

11. 12/7/2018
SQL examples(1)
List the first letters of members’ last name and a count of the number of members for each
SELECT Left(lastname,1), Count(*)
FROM Members
GROUP BY Left(lastname,1)
6. Functions CS1222_F2018

12. SQL examples(2) Find out which track has the longest track name
12/7/2018
SQL examples(2)
Find out which track has the longest track name
SELECT Tracktitle
FROM Tracks
WHERE Length(Tracktitle)=(
SELECT Max(Length(Tracktitle))
FROM Tracks)
6. Functions CS1222_F2018

13. 12/7/2018
SQL examples(3)
For any artist whose name begins with ‘The ‘, list the name formatted as: Rolling Stones, The
SELECT Concat(Right(artistName,Length(artistName)-
4), ', The' ) AS NewName
FROM Artists
WHERE Left(artistName,4) = 'The ‘
NewName
———————
Neurotics, The
Bullets, The
Kicks, The
6. Functions CS1222_F2018

14. 12/7/2018
SQL Example (4)
Report a list of all of the domains that are used by members for . The domain is the part of the address after
SELECT Right( , Length( )-
FROM Members
WHERE IS NOT NULL
6. Functions CS1222_F2018

15. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

16. Date Manipulation in MySQL
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Date Manipulation in MySQL
6. Functions CS1222_F2018

17. MySQL Date_Format Format string may include literals
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MySQL Date_Format
Format string may include literals
Enclose entire format string in quotes.
6. Functions CS1222_F2018

18. 12/7/2018
DATEDIFF(expr1,expr2)
DATEDIFF(expr1,expr2) returns the number of days between the start date expr1 and the end date expr2.
expr1 and expr2 are date or date-and-time expressions.
Only the date parts of the values are used in the calculation.
mysql> SELECT DATEDIFF(' :59:59',' ');
-> 1
mysql> SELECT DATEDIFF(' :59:59',' ');
> -31
6. Functions CS1222_F2018

19. MySQL Date_Format ADDDATE('2004-12-01',INTERVAL 1 YEAR) '2005-12-01'
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MySQL Date_Format
ADDDATE(' ',INTERVAL 1 YEAR) ' '
ADDDATE(' ',INTERVAL 60 DAY) ' '
ADDDATE(' ',INTERVAL -3 MONTH) ' '
DATE_FORMAT(' ','%M %e, %Y')
'December 1, 2004'
DATE_FORMAT(' ','The %D of %M')
'The 1st of December'
6. Functions CS1222_F2018

20. Date Manipulation Example(1)
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Date Manipulation Example(1)
List the names and birthdays of all members with June birthday
SELECT lastname, firstname,
birthday
FROM Members
WHERE Month(birthday)=6
6. Functions CS1222_F2018

21. Date Manipulation Example(2)
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Date Manipulation Example(2)
List each artist name and that artist’s one-year anniversary date.
SELECT artistName,
AddDate(entrydate, Interval 1 Year)
AS Anniversary
FROM Artists
6. Functions CS1222_F2018

22. Date Manipulation Example(3)
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Date Manipulation Example(3)
Report the age in days of members from Georgia.
Select lastname, firstname, birthday, To_Days(Now())-To_days(birthday) As AgeInDays
From Members
Where region='GA'
6. Functions CS1222_F2018

23. Date Manipulation Example(4)
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Date Manipulation Example(4)
Report the artistname and entry date of each artist in mm-dd-yyyy format.
Select artistname, entrydate,
Date_Format(entrydate, '%m-%d-%Y')
As Entered
From Artists
6. Functions CS1222_F2018

24. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

25. Handling Nulls in MySQL
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Handling Nulls in MySQL
IsNull() returns true or false depending on if expression is null
IsNull(expression)
IfNull() reports replacement value if expression is null
IfNull(expression, display_if_expression_is_null)
6. Functions CS1222_F2018

26. 12/7/2018
Example 1
List the web address of each artist and whether or not the web address is null.
Select WebAddress, IsNull(WebAddress)
As Is_It_Null
From Artists
6. Functions CS1222_F2018

27. 12/7/2018
Example 2
List the web address of each artist. If the web address is null, list ‘No website.‘
Select webaddress,
IfNull(WebAddress,'No website')
From Artists
6. Functions CS1222_F2018

28. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

29. Data type Conversions in MySQL
12/7/2018
Data type Conversions in MySQL
MySQL automatically handles datatype conversions
Select Concat(trackTitle, ':', lengthSeconds)
From Tracks
Where titleID = 4
6. Functions CS1222_F2018

30. Objectives Concatenate text fields Text and data manipulation
12/7/2018
Objectives
Concatenate text fields
Text and data manipulation
Date manipulation
Manipulate null values
Data type conversion
Misc functions
6. Functions CS1222_F2018

31. 12/7/2018
Simple Case
6. Functions CS1222_F2018

32. Simple Case Example Select Artistname, Region, Case Region
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Simple Case Example
Select Artistname, Region,
Case Region
When 'NC' Then 'South'
When 'VA' Then 'South'
When 'IL' Then 'Midwest'
When 'VT' Then 'New England'
Else 'Somewhere Else'
End As Area
From Artists
Artistname Region Area
The Neurotics NC South
Louis Holiday IL Midwest
Word IN Somewhere Else
Sonata VA South
The Bullets TX Somewhere Else
Jose MacArthur CA Somewhere Else
Confused GA Somewhere Else
The Kicks NY Somewhere Else
Today ONT Somewhere Else
21 West Elm VT New England
Highlander OH Somewhere Else
6. Functions CS1222_F2018

33. Searched Case Syntax SELECT Field, Field, CASE
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Searched Case
Syntax
SELECT Field, Field,
CASE
WHEN Field | Expression comparison Value | Field | Expression THEN result
ELSE result
END As alias
FROM Table
6. Functions CS1222_F2018

34. 12/7/2018
Searched Case
List the first two tracks of each title, identifying short 1st tracks and long 1st tracks.
Select TrackNum, TrackTitle, LengthSeconds,
Case
When TrackNum=1 And LengthSeconds<240 Then 'Short 1st'
When TrackNum=1 And LengthSeconds>480 Then 'Long 1st'
Else 'Another Track'
End as Eval
From Tracks
Where TrackNum<3
6. Functions CS1222_F2018

35. 12/7/2018
Greatest(num1, num2,…)
List the largest of the following numbers: 3,5,7,9
Select Greatest(3,5,7,9)
6. Functions CS1222_F2018

36. 12/7/2018
Least(num1, number2,…)
List any tracks that lack either an mp3 or Real Audio recording
Select trackTitle, mp3, realAud
From Tracks
Where Least(mp3, realAud)=0
6. Functions CS1222_F2018

37. 12/7/2018
FORMAT(X,D)
Formats the number X to a format like '#,###,###.##', rounded to D decimals, and returns the result as a string. If D is 0, the result will have no decimal point or fractional part.
mysql> SELECT FORMAT( , 4);
-> '12, ‘
mysql> SELECT FORMAT( ,4);
-> '12, '
mysql> SELECT FORMAT( ,0);
-> '12,332'
6. Functions CS1222_F2018

38. 12/7/2018
Example
Report the name and yearly base of each salesperson formatted with commas and two decimal places
Select Concat(firstname, ' ', lastname), Format(base*52 * 5, 2) as 'Yearly Salary'
From SalesPeople
6. Functions CS1222_F2018

39. Summary Text functions Concatenation: Concat, Concat_WS
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Summary
Text functions
Concatenation: Concat, Concat_WS
String length: Length
Substring extract: Left, Right, Substring
Substring manipulation
LTrim, RTrim, Trim, Upper, Lower
Substring search: Locate
6. Functions CS1222_F2018

40. Summary (Cont.) Date manipulation Handle Null values: IsNULL, IfNULL
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Summary (Cont.)
Date manipulation
Now, Date, day, month,year….
AddDate, DateDiff,SubDate
Handle Null values: IsNULL, IfNULL
Misc functions
Case, Greatest, Least, Format
6. Functions CS1222_F2018