我有表(大约 80'000 行),看起来像
id, parentId, col1, col2, col3...
1, null, 'A', 'B', 'C'
2, 1, ...
3, 1, ...
4, null, ...
5, 4, ...
(一级父母 - 仅限儿童)
我需要获取所有相关行 -
SELECT ...
FROM table
WHERE id = :id OR parentId = :id OR id IN (
SELECT parentId
FROM table
WHERE id = :id
)
但是为什么这个请求工作缓慢而不是 2 请求 - 如果我先在 php 上获得 parentId?
$t = executeQuery('SELECT parentId FROM table WHERE id = :Id;', $id);
if ($t) {
$id = $t;
}
$t = executeQuery('SELECT * FROM table WHERE id = :id OR parentId = :id ORDER BY id;', $id);
PS:最大取决于行 < 70
PP:
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY product ALL PRIMARY,parentId NULL NULL NULL 73415 Using where
2 DEPENDENT SUBQUERY product const PRIMARY,parentId PRIMARY 4 const 1