如何在PHP Mongo中查询空字符串？

Question

I'd like to query for all documents in my collection where the field client is an empty string. I've seen plenty of examples of how to check if something's not an empty string but I can't find any examples of how to do the opposite. I've tried db.collection.find({client: ""}) but I get back an empty set.

EDIT: The example entry in the collection looks like

{ "_id" : ObjectId("54eb59699e12a795078b80da"), "reportID" : "1472031", "orgID" : "336", "client" : "", "customerID" : NumberLong(1), "address" : "123 main st", "city" : "Grove City", "state" : "OH", "zip" : "43123", "county" : "Franklin", "gpsLatitude" : null, "gpsLongitude" : null, "dateDue" : ISODate("2012-08-18T00:00:00Z"), "dateDueClient" : ISODate("2012-08-18T00:00:00Z"), "dateComplete" : ISODate("2012-08-18T00:00:00Z"), "dateCompleteEstimate" : NumberLong(0), "contractorSubmissionDate" : ISODate("2012-08-19T00:26:23Z"), "createdOn" : ISODate("2012-08-19T00:21:37Z"), "assignedToContractorOn" : ISODate("2012-08-19T00:21:37Z"), "workTypeID" : "6338", "assignedAdmin" : "7880", "contractorID" : "7880", "categoryID" : "0", "historyLength" : NumberLong(0), "invoiceDate" : ISODate("2012-08-18T00:00:00Z"), "submittedToClient" : ISODate("2012-08-18T00:00:00Z"), "paymentContractor" : NumberLong(0), "paymentClient" : NumberLong(0), "contractorIsPaid" : NumberLong(0), "clientIsPaid" : NumberLong(0), "sentinel" : NumberLong(1), "isFrozen" : NumberLong(0), "numTimesClientReady" : "1", "pcrResponses" : [ ] }

There's a lot of fields but the client one is pretty close to the beginning.

Answer 1

The query you posted should work. Just to verify, I inserted that data as a row in a test collection, and it was returned right back out with db.test.find({client: ''})

I'm thinking you may have a problem somewhere else. I've once or twice been in the wrong database when running queries, or had a typo in the collection name. To verify what my data looks like, I'll often times:

> db.tset.find({client: ''});
[] // What? No results? ...backspacebackspacebackspace

> db.tset.find();
[] // What? No results at all for no query? I must be in the.. OH!

> db.test.find();
[] // What? I thought I had a typo in my collection name. What database am I in?

> db
tseting // OH! I keep making that typo..

> use testing
switched to db testing

> db.test.find({client: ''});
[] // What? Still no results? This is weird...

> db.test.insert({client: ''});

> db.test.find({client: ''});
{ "_id" : ObjectId("54f1b5e5d05052fce4fb6684"), "client" : "" }
// Hmm, ok, so there's nothing wrong with the query. The data came up
// So I'm still just in the wrong place? Really?
// Maybe I woke up on the wrong side of the bed today. I should eat lunch.

Sometimes tunnel vision makes you think the problem lies somewhere that it doesn't. Leave a comment if this is or isn't helpful, maybe we can come up with some more troubleshooting ideas.