SQLZOO wrong question highlights

** SELECT names **

1. Find the countries that have three or more a in the name
   SELECT name FROM world WHERE name LIKE '%a%a%a%';

2. Find the country where the name is the capital city.
   SELECT name FROM world WHERE name = capital;#这里可以直接在一条记录的不同列值之间进行比对
   

3. Find the country where the capital is the country plus "City".
   SELECT name,capital FROM world WHERE capital = concat(name,' ','city');#可以在WHERE语句中添加函数条件
   

4. 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,'%');#这里用concat生成一个统配字符串
   

5.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 name,capital from world where capital like concat(name,'_%')#_通配符只能匹配1个字符，%可以匹配0个字符

6.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.
select name,replace(capital, name, '') from world where capital Like concat(name,'%_')；#这里的replace函数也可以直接识别变量