3.3

String Functions

CONCAT

  • Combines a list of strings into a single string.
  • Can include column values and literal values.
  • In MySQL literal values can be enclosed with either single ( ‘ ) or double quotes ( “ ) .

Example:

USE world;
SELECT CONCAT(name, ', ', continent)
FROM country;

Results:

07_functions.png

RIGHT, LEFT

  • The RIGHT and LEFT functions have two parameters. The first is a string and the second is the number of characters to be returned.
  • The RIGHT function starts counting from the right side of the string. • The LEFT function starts counting from the left side of the string.

Table 7. RIGHT, LEFT functions

Function Type Example Result

RIGHT(string, num. characters)

string

RIGHT(‘Salmon’, 3)

mon

LEFT(string, num. characters)

string

LEFT(‘Salmon’, 3)

Sal

Example:

USE bike;
SELECT category_name, 
    LEFT(category_name, 8) AS 'First 8 Characters',
    RIGHT(category_name, 8) AS 'Last 8 Characters'
FROM category;

Results:

08_functions.png

TRIM, LTRIM, RTRIM

  • The TRIM function will remove leading and trailing spaces from a string.
  • The LTRIM function will remove leading spaces from a string.
  • The RTRIM function will remove trailing spaces from a string.

Table 8. TRIM functions

Function Type Example Result

TRIM(string)

string

TRIM(‘   Salmon  ‘)

‘salmon’

LTRIM(string)

string

LEFT(‘Salmon   ‘)

‘salmon  ’

RTRIM(string)

string

RIGHT(‘  Salmon‘)

‘  salmon’

Example:

SELECT LTRIM('  Salmon  ') AS "Left Trim",
    RTRIM('  Salmon  ') AS "Right Trim",
    TRIM('  Salmon  ') AS "Trim";

Results:

09_functions.png

FORMAT

  • FORMAT() accepts a decimal but returns a comma formatted string.

Table 9. FORMAT functions

Function Type Example Result

FORMAT(number, decimal)

string

FORMAT(1234.342, 2)

-356

Code Sample:

SELECT FORMAT(list_price,2) 
FROM bike.product;

Results:

10_functions.png

LOWER, UPPER

  • LOWER() converts all characters to lower case.
  • UPPER() converts all characters to upper case.

Table 9. LOWER, UPPER functions

Function Type Example Result

LOWER(string)

string

LOWER(‘Salmon ‘)

‘salmon’

UPPER(string)

string

UPPER(‘Salmon‘)

‘SALMON’

Example:

SELECT UPPER('Salmon'), 
    LOWER('Salmon');

Results:

11_functions.png

LOCATE, LENGTH, SUBSTRING

LOCATE(), and LENGTH() accept a string but return an integer. • SUBSTRING() accepts a string and returns a string.

Table 9. LOCATE. LENGTH, SUBSTRING functions

Function Type Example Result

LOCATE(find,search[,start])

string

LOCATE(‘al’,’salmon’,1)

2

LENGTH(str)

string

LENGTH(‘salmon’)

6

SUBSTRING(str,start[,length])

string

SUBSTRING('salmon',3,999)

‘lmon’

Example:

SELECT LOCATE('al','salmon',1), 
    LENGTH('salmon'), 
    SUBSTRING('salmon',3,999);

Results:

12_functions.png

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