转换为加入
我有一个效率相当低的查询，我认为我可以使用 SQL JOIN 来减少它。
这是两个查询：
$data = $db->query("SELECT * from tbl_forums_threads WHERE tid = '$id'");
$threaddata = $data->fetch_assoc();
$dataset = $db->query("SELECT * from tbl_forums_posts WHERE tid = '$id'");
$thread = $dataset->fetch_assoc();
显然，它们有 1 个共同点：使用 $id。
我可以使用 SQL JOIN 甚至 LEFT JOIN 吗？
谢谢！
I've got a query that's rather inefficient, and I think that I can use SQL JOIN to cut it down.
Here are the two queries:
$data = $db->query("SELECT * from tbl_forums_threads WHERE tid = '$id'");
$threaddata = $data->fetch_assoc();
$dataset = $db->query("SELECT * from tbl_forums_posts WHERE tid = '$id'");
$thread = $dataset->fetch_assoc();
Obviously, they have 1 thing in common: the use of $id.
Could I use SQL JOIN, or even LEFT JOIN?
Thanks!
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通过在每个表的
tid列上创建索引，您可以获得比更改查询更好的改进。使用基本 where 子句对单个表进行简单的
select应该不会很慢；如果是，可能是因为他们没有使用索引。在这种情况下，您只过滤一个字段，因此这是需要索引的唯一可能性。You'd get far better improvements by creating indices on the
tidcolumn in each table than you would by changing the queries.Simple
selects on a single table with a basic where clause should not be slow; if they are, it's probably because they're not using an index. In this case, you're only filtering on one field, so that's the only possibility for needing an index.1 个带有 JOIN 的 SQL 查询不一定比 2 个这样的简单查询更快。
在我看来，留下来吧。
1 SQL query with a JOIN isn't necessarily faster than a 2 simple query like that.
Stay with this imo.