MongoDB $或查询 [英] MongoDB $or query

问题描述

我在mongo shell中运行以下查询:

I run following query in mongo shell:

db.Profiles.find ( { $or: [ {"name": "gary"}, {"name": "rob"} ] } )

它只是不返回预期的(JSON)吗?

It just returns nothing as expected(JSON)?

推荐答案

使用$ in

对于问题中的查询，更适合使用 $ in

db.Profiles.find ( { "name" : { $in: ["gary", "rob"] } } );

为什么不起作用

缺少引号-cli正在等待您完成或"的第二部分:

Why doesn't it work

There's a missing quote - the cli is waiting for you to finish the second part of your or:

db.Profiles.find ( { $or : [ { "name" : "gary" }, {"name":"rob} ] } )
..............................................................^

您需要充分完成查询，以便cli对其进行解析，然后再说出语法错误.

You need to finish the query sufficiently for the cli to parse it for it to then say there's a syntax error.

如注释所示，如果要以不区分大小写的方式进行搜索，则可以将$or与

As indicated by a comment, if you want to search in a case insensitive manner, then you either use $or with a $regex:

db.Profiles.find ( { $or : [ { "name" : /^gary/i }, {"name": /^rob/i } ] } )

或者，您只需使用一个正则表达式:

Or, you simply use one regex:

db.Profiles.find ( { "name" : /^(gary|rob)/i } )

但是，不是以固定字符串开头的正则表达式查询不能使用索引(它不能使用索引，并且实际上会执行从此处开始，直到找不到匹配项然后保释")，因此是次优的.如果这是您的要求，则最好存储一个规范化的名称字段(例如name_lc-小写名称)并在该字段上进行查询:

However, a regex query that doesn't start with a fixed string cannot use an index (it cannot use an index and effectively do "start here until no match found then bail") and therefore is sub-optimal. If this is your requirement, it's a better idea to store a normalized name field (e.g. name_lc - lower case name) and query on that:

db.Profiles.find ( { "name_lc" : { $in: ["gary", "rob"] } } );

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