Random MongoDb Syntax: Updates
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by Liam McLennan
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Published on Tue, 01 Jun 2010 18:15:03 GMT
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2010/06/02
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I have a MongoDb collection called tweets. Each document has a property system_classification. If the value of system_classification is ‘+’ I want to change it to ‘positive’.
For a regular relational database the query would be:
update tweets set system_classification = 'positive' where system_classification = '+'
the MongoDb equivalent is:
db.tweets.update({system_classification: '+'},
{$set: {system_classification:'positive'}}, false, true)| Parameter | Description |
|
{ system_classification: '+' } |
the first parameter identifies the documents to select |
|
{ $set: { system_classification: 'positive' } } |
the second parameter is an operation ($set) and the parameter to that operation {system_classification: ‘positive’} |
| false | the third parameter indicates if this is a regular update or an upsert (true for upsert) |
| true | the final parameter indicates if the operation should be applied to all selected documents (or just the first) |
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