從mysql表中刪除選定的行

Question

從表中刪除此選擇的結果的最佳方法是什麼？

select id from taxon2 as a 
    where rank = 'No Taxon' and 
    (select count(*) from taxon2 as b 
     where a.id = b.parentid) = 0; 

Answer 1

這裏是具有OUTER JOIN的溶液：

delete taxon2 
from taxon2 
    left join taxon2 t2 on taxon2.id = t2.parentid 
where t2.id is null; 

• SQL Fiddle Demo

並與NOT EXISTS：

delete from taxon2 
where rank = 'No Taxon' 
    and not exists (
     select 1 
     from (select * from taxon2) as b 
     where b.parentid=taxon2.id) 

• More Fiddle