FROM db WHERE A = const AND B > const AND C >= const ORDER BY B DESC LIMIT constSELECTFROM db' WHERE A' = const ORDER BY X' DESC LIMIT const
关于第一次查询的问题:有一个多行索引(A、B、C)还是因为ORDER BY语句需要额外的单行索引关于第二个查询的问题:我需要一个多行索引(A',X
我有c.name和r.scope的全文索引 INNER JOIN categories c on r.id = c.result_idINNER JOIN tags t on r.id = t.result_id
WHERE c.name in ('purchase', 'single_family'r.scope = 'all' OR r.scope =
我应该在表上创建什么索引,这样查询才能使用索引并避免使用临时和文件排序?我尝试了许多不同的索引组合,并阅读了,但我似乎无法理解它。我的解释要么是Using Where (无索引),要么是Using Where Using Temporary, Using FilesortFROM table AND c4 = 2011
AND
这两个mysql查询的区别是什么(select count(c.id) from comment c where c.topic_id = t.id) as comments_countfrom topic;select t.id,comments.count from topic(
select count(c.id) count,c.topic_idfrom comment c group by topi
我有一个MySQL表T,列c1上有一个索引。我的连接查询如下所示。select something from T as t1 inner join T as t2 on ABS(t1.c1-t2.c1)<2;
我使用explain来查看MySQL是否使用索引。上面的查询没有使用索引。但它确实为下面的查询使用了索引。select something from T as t1 inner join T as t2 on t1.<em
具有以下查询,其中第一个查询返回找到的行数字段,第二个查询返回实际行数:SELECT count(*) as total FROM individual i WHERE i.hid=:hhid AND i.hihh=:answer$sql = "SELECT *
individual i i.hid=:hhid i.hihh=:answer";
$exec->bindValu