Difference between revisions of "SELECT names"

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(Pattern Matching Strings)
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<source lang='sql' class='ans'>
 
<source lang='sql' class='ans'>
SELECT name, capital FROM world
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SELECT capital,name FROM world
 
  WHERE capital LIKE concat(name, '_%')
 
  WHERE capital LIKE concat(name, '_%')
 
</source>
 
</source>

Revision as of 02:20, 30 May 2017

Language: English  • 中文
namecontinent
AfghanistanAsia
AlbaniaEurope
AlgeriaAfrica
AndorraEurope
AngolaAfrica
....



Pattern Matching Strings

This tutorial uses the LIKE operator to check names. We will be using the SELECT command on the table world:

You can use WHERE name LIKE 'B%' to find the countries that start with "B".

  • The % is a wild-card it can match any characters

Find the country that start with Y

SELECT name FROM world
  WHERE name LIKE 'F%'
SELECT name FROM world
  WHERE name LIKE 'Y%'


Find the countries that end with y

SELECT name FROM world
  WHERE name LIKE 'T%'
SELECT name FROM world
  WHERE name LIKE '%y'

Luxembourg has an x - so does one other country. List them both.

Find the countries that contain the letter x

SELECT name FROM world
  WHERE name LIKE 'T%'
SELECT name FROM world
  WHERE name LIKE '%x%'

Iceland, Switzerland end with land - but are there others?

Find the countries that end with land

SELECT name FROM world
  WHERE name LIKE 'T%'
SELECT name FROM world
  WHERE name LIKE '%land'

Columbia starts with a C and ends with ia - there are two more like this.

Find the countries that start with C and end with ia

SELECT name FROM world
  WHERE name LIKE 'T%'
SELECT name FROM world
  WHERE name LIKE 'C%ia'

Greece has a double e - who has a double o?

Find the country that has oo in the name

SELECT name FROM world
  WHERE name LIKE '%ee%'
SELECT name FROM world
  WHERE name LIKE '%oo%'

Bahamas has three a - who else?

Find the countries that have three or more a in the name

SELECT name FROM world
  WHERE name LIKE 'T%'
SELECT name FROM world
  WHERE name LIKE '%a%a%a%'

India and Angola have an n as the second character. You can use the underscore as a single character wildcard.

SELECT name FROM world
 WHERE name LIKE '_n%'
ORDER BY name

Find the countries that have "t" as the second character.

SELECT name FROM world
 WHERE name LIKE '_n%'
ORDER BY name
SELECT name FROM world
 WHERE name LIKE '_t%'
ORDER BY name

Lesotho and Moldova both have two o characters separated by two other characters.

Find the countries that have two "o" characters separated by two others.

SELECT name FROM world
 WHERE name LIKE '_n%'
SELECT name FROM world
 WHERE name LIKE '%o__o%'

Cuba and Togo have four characters names.

Find the countries that have exactly four characters.

SELECT name FROM world
 WHERE name LIKE 'Cu%'
SELECT name FROM world
 WHERE name LIKE '____'

Harder Questions

Well done for getting this far.

The next questions are optional and only for students who are finding the basic questions too easy.

The capital of Luxembourg is Luxembourg. Show all the countries where the capital is the same as the name of the country

Find the country where the name is the capital city.

SELECT name, capital, continent
  FROM world
 WHERE name LIKE '%x%'
SELECT name FROM world
 WHERE name = capital

The capital of Mexico is Mexico City. Show all the countries where the capital has the country together with the word "City".

Find the country where the capital is the country plus "City".

The function concat is short for concatenate - you can use it to combine two or more strings.

SELECT name, concat(name, 'town')
  FROM world
 WHERE name LIKE '%ina%'
SELECT name FROM world
 WHERE capital = concat(name, ' City')

Find the capital and the name where the capital includes the name of the country.

SELECT capital, name FROM world
 WHERE capital LIKE concat('%', name, '%')

Find the capital and the name where the capital is an extension of name of the country.

You should include Mexico City as it is longer than Mexico. You should not include Luxembourg as the capital is the same as the country.

SELECT capital,name FROM world
 WHERE capital LIKE concat(name, '_%')

For Monaco-Ville the name is Monaco and the extension is -Ville.

Show the name and the extension where the capital is an extension of name of the country.

You can use the SQL function REPLACE.

select name,mid(capital,length(name)+1) ext
from world
where capital like concat(name,'_%')