[英]How can I convert regexp to like?
I came across this question and apparently regexp are much slower than like. 我遇到了这个问题,显然regexp比它慢得多。 MySQL regexp much slow than like
MySQL的正则表达式比喜欢慢得多
How can I convert the following regexp to like? 如何将以下正则表达式转换为like?
WHERE category REGEXP '[[:<:]](5|50|51|52|53|54|55|56|57|58|59|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99|100|101|102|103|104|105|106|107|108|109|110|111|112|113|114|115|116|117|118|119|120|121|122|123|124|125|126|127|128|129|130|131|132|133|134|135|136|137|138|139|140|141|142|143|144|145|146|147|148|149|150|151|152|153|154|155|156|157|158|159|160|161|162|163|164|165|166|167|168|169|170|171|172|173|174|175|176|177|178|179|180|181|182|183|184|185|186|187|188|189|190|191|192|193|194|195|196|197|198|199|200|201|202|203|204|205|206|207|208|209|210|211|212|213|214|215|216|217|218|219|220|221|222|223|224|225|226|227|228|229|230|231|232|233|234|235|236|237)[[:>:]]'
categories stored the following way per post: 每个帖子按以下方式存储类别:
15,19,66,12
This is not a direct answer to your question. 这不是您问题的直接答案。 Instead, it is a brief explanation of how data structures should be stored in SQL.
相反,它简要说明了如何在SQL中存储数据结构。
You are storing a comma delimited list of categories on each row. 您将在每行上存储以逗号分隔的类别列表。 You then want to see if one of a large set of categories are in the list.
然后,您要查看列表中是否包含大量类别中的一个。 The appropriate data structure is an association table between the two.
适当的数据结构是两者之间的关联表。 It would be defined as something like:
它将定义为:
create table ItemCategory (
ItemCategoryId int auto_increment not null,
ItemId int not null,
CategoryId int not null
);
Then, when you want a comma delimited list, you would do: 然后,当您想要用逗号分隔的列表时,可以这样做:
select ic.ItemId, group_concat(ic.CategoryId) as categories
from ItemCategory ic
group by ic.ItemId;
When you wanted to find items that have one of a large set of categories: 当您想要查找具有大量类别之一的项目时:
select distinct ItemId
from ItemCategory ic
where ic.CategoryId in (<long list here>);
Then if you have an index on CategoryId
, this will use the index and perform well. 然后,如果您在
CategoryId
上有一个索引,它将使用该索引并且性能良好。
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