Where can I find or condition in MongoDB?
Mongo currently does not include an OR operator for such queries, however there are ways to express such queries. Use “in” or “where”. Using a $where query will be slow, in part because it can’t use indexes.
What is where clause in MongoDB?
The MongoDB $where operator is used to match documents that satisfy a JavaScript expression. A string containing a JavaScript expression or a JavaScript function can be pass using the $where operator. The JavaScript expression or function may be referred as this or obj.
How do I find a specific value in MongoDB?
“how to find specific value in mongodb” Code Answer’s
- var name = req. params. name;
- var value = req. params. value;
- var query = {};
- query[name] = value;
- collection. findOne(query, function (err, item) { });
How or condition works in MongoDB?
MongoDB provides different types of logical query operators and $or operator is one of them. This operator is used to perform logical OR operation on the array of two or more expressions and select or retrieve only those documents that match at least one of the given expression in the array.
How do I view a database in MongoDB?
If you want to check your databases list, use the command show dbs. Your created database (mydb) is not present in list. To display database, you need to insert at least one document into it. In MongoDB default database is test.
What does find return in MongoDB?
find() returns the cursor of Result Set of a query by which you can iterate over the result set or print all documents.
How do I show collections in MongoDB?
To obtain a list of MongoDB collections, we need to use the Mongo shell command show collections . This command will return all collections created within a MongoDB database. To be able to use the command, we’ll first need to select a database where at least one collection is stored.
Where is array data in MongoDB?
To query if the array field contains at least one element with the specified value, use the filter { : } where is the element value. To specify conditions on the elements in the array field, use query operators in the query filter document: { : { : , } }
What is projection in MongoDB?
MongoDB provides a special feature that is known as Projection. It allows you to select only the necessary data rather than selecting whole data from the document.
How do I test multiple values in MongoDB?
MongoDB provides the find() that is used to find multiple values or documents from the collection. The find() method returns a cursor of the result set and prints all the documents. To find the multiple values, we can use the aggregation operations that are provided by MongoDB itself.
Is null in MongoDB?
MongoDB fetch documents containing ‘null’ If we want to fetch documents from the collection “testtable” which contains the value of “interest” is null, the following mongodb command can be used : >db. In the first document, the value of ‘interest’ is ‘null’ but in the second one ‘interest’ column does not exist.
How does the where condition work in MongoDB?
The WHERE condition fetches data based on a particular value that matches to the available data in the collection. The AND condition displays only those records where both condition 1 and condition 2 are met. The OR condition displays those records if any one of the conditions is met.
When to use GT or in in MongoDB?
Therefore, query performance improves when you express your query using the standard MongoDB operators (e.g., $gt, $in ). In general, you should use $where only when you cannot express your query using another operator. If you must use $where, try to include at least one other standard query operator to filter the result set.
How to do a database query in MongoDB?
What Is a Database Query? 1 Methods for Performing Queries in MongoDB. The find () method: This method is used for querying data from a MongoDB collection. 2 Filtering Criteria in MongoDB Queries. 3 MongoDB Query Which Specify “AND” Condition. 4 MongoDB Query Which Specify “OR” Condition. 5 $in operator.
Which is an example of a special operator in MongoDB?
MongoDB allows users to specify either one or multiple values to be true. According to this, till one of the conditions is true, the document data will get returned. Here is an example showing the use of OR condition: The $in operator is another special operator used in queries for providing a list of values in the query.