Overview of Filter Comparison Operators

A comparison operator tests whether a given JSON object field satisfies some conditions.

One of the simplest and most useful filter specifications tests a field for equality to a specific value. For example, this filter specification matches any document that has a field name whose value is "Jason". It uses the operator $eq, which tests field-value equality.

{ "name" : { "$eq" : "Jason" } }

For convenience, for such a scalar-equality filter you can generally omit operator $eq. This scalar-equality filter specification is thus equivalent to the preceding one, which uses $eq:

{ "name" : "Jason" }

Both of the preceding filter specifications match Example 2-1.

The comparison operators are the following:

$all — whether an array field value contains all of a set of values
$between — whether a field value is between two string or number values (inclusive)
$eq — whether a field value is equal to a given scalar
$exists — whether a given field exists
$gt — whether a field value is greater than a given scalar value
$gte — whether a field value is greater than or equal to a given scalar
$hasSubstring — whether a string field value has a given substring (same as $instr)
$in — whether a field value is a member of a given set of scalar values
$instr — whether a string field value has a given substring (same as $hasSubstring)
$like — whether a field value matches a given SQL LIKE pattern
$lt — whether a field value is less than a given scalar value
$lte — whether a field value is less than or equal to a given scalar value
$ne — whether a field valueis different from a given scalar value
$nin — whether a field value is not a member of a given set of scalar values
$regex — whether a string field value matches a given regular expression
$startsWith — whether a string field value starts with a given substring

You can combine multiple comparison operators in the object that is the value of a single filter field. The operators are implicitly ANDed. For example, the following filter uses comparison operators $gt and $lt. It matches Example 2-2, because that document contains an age field with a value (50), which is both greater than 45 and less than 55.

{ "age" : { "$gt" : 45, "$lt" : 55 } }

Both the operand of a SODA operator and the data matched in your documents by a filter are JSON data. But a comparison operator can in some cases interpret such JSON values specially before comparing them. The use of item-method operators can specify that a comparison should first interpret JSON string data as, for example, uppercase or as a date or a time stamp (date with time). This is explained in the sections about item-method operators.

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