Tag: how to

Rename a Field in the Query Results in MongoDB

Posted on by Ian

Sometimes when you query a collection in MongoDB, you might not be happy with the field names. By default, the field names are simply a reflection of the field names in the actual documents.

Perhaps the field names are inconsistent, or there’s a typo. Whatever the reason, you can use the $project aggregation pipeline stage to rename a field in your query results.

In some ways, this is comparable to using an alias in SQL, as it doesn’t rename the underlying fields, it simply renames them in the query results.

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How to Fix “The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION” in SQL Server

Posted on by Ian

If you’re receiving error Msg 3902, Level 16, which reads “The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION”, it’s probably because you’ve got a stray COMMIT statement.

You could be getting this due to implementing error handling, and forgetting that you’ve already committed or rolled back the transaction elsewhere in your code.

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How to Create an Index with a Specific Name in MongoDB

Posted on by Ian

When you create an index in MongoDB, if you don’t specify a name for it, MongoDB will assign one.

The default name consists of each indexed field name concatenated with the key value for that field. For example, the sort order, or if it’s a text index, the string _text, or if it’s a 2dsphere index, the string _2dsphere, etc.

But you can assign your own name when creating indexes in MongoDB.

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Exclude Specific Fields in Wildcard Index in MongoDB

Posted on by Ian

When you create a wildcard index in MongoDB, you have the option of specifying a single field, all fields, or just some.

You also have the option of excluding certain fields. In other words, you can specify all fields except for one or more specific fields.

You can use the wildcardProjection parameter to include or exclude specific field paths from the wildcard index. This article presents an example of excluding specific fields in the wildcard index.

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Create a Multi-Language Text Index in MongoDB

Posted on by Ian

When you create a text index in MongoDB, the index uses a default language of english.

The default language determines the rules to parse word roots (i.e. stemming) and ignore stop words.

However, you can change the default language if required.

You can also specify a language at the document level, and even at the subdocument level. The default language will only be used if a language hasn’t been specified at the document or subdocument level.

This article presents examples of specifying a language for a text index.

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