Introduction1. How to Retrieve Data From a Single Table1.1. The Five Clauses of the SELECT Statement1.2. Column Specifications1.3. LIKE and REGEXP Operators1.4. Arithmetic Operators1.5. Column Aliases1.6. Comparison Operators1.7. IS NULL, BETWEEN, IN Operators1.8. AND, OR, NOT Logical Operators1.9. DISTINCT Clause2. How to Retrieve Data from Multiple Tables2.1. The JOIN Clause2.2. Joining More Than Two Tables2.3. The OUTER JOIN Clause2.4. How to Code a UNION3. Using Functions3.1. Date Functions3.2. Numeric Functions3.3. String Functions4. How to Insert, Update, Delete Data in Tables4.1. The INSERT Clause With a Column List4.2. The INSERT Clause Without a Column List4.4. The UPDATE Clause With a Column List4.4. The DELETE Clause5. Summary Queries and Aggregate Functions5.1. Aggregate Functions5.2. Grouping Data5.3. Simple GROUP BY Query5.4. Improving the GROUP BY Query5.5. Using the HAVING Clause5.5. Using the HAVING and WHERE Clauses Together5.6. COUNT(column_name) and COUNT(*)5.7. Using the DISTINCT Statement6. Working With Subqueries6.1. The Subquery In a SELECT Statement6.2. The Subquery in an UPDATE statement6.3. Create a Duplicate Table From An Existing Table 6.4. The Subquery In a Delete Statement7. SQL Views7.1. SQL View Explained7.2. Benefits of Using Views7.3. Views That Allow UPDATE Statements8. SQL Indexes8.1. SQL Indexes Explained8.2. Clustered vs. Non-clustered Indexes8.3. Create an Index in Workbench Using an ERD8.4. How to Manually Add an Index to an Existing TableGlossaryIndex
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

End-of-Chapter Survey

: How would you rate the overall quality of this chapter?
  1. Very Low Quality
  2. Low Quality
  3. Moderate Quality
  4. High Quality
  5. Very High Quality
Comments will be automatically submitted when you navigate away from the page.