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Update Operators¶
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The following modifiers are available for use in update operations; e.g. in db.collection.update() and db.collection.findAndModify().
Specify the operator expression in a document of the form:
{
<operator1>: { <field1>: <value1>, ... },
<operator2>: { <field2>: <value2>, ... },
...
}
注解
For details on specific operator, including syntax and examples, click on the specific operator to go to its reference page.
Update Operators¶
Fields¶
| Name | Description |
|---|---|
| $inc | Increments the value of the field by the specified amount. |
| $mul | Multiplies the value of the field by the specified amount. |
| $rename | Renames a field. |
| $setOnInsert | Sets the value of a field if an update results in an insert of a document. Has no effect on update operations that modify existing documents. |
| $set | Sets the value of a field in a document. |
| $unset | Removes the specified field from a document. |
| $min | Only updates the field if the specified value is less than the existing field value. |
| $max | Only updates the field if the specified value is greater than the existing field value. |
| $currentDate | Sets the value of a field to current date, either as a Date or a Timestamp. |
Array¶
Operators¶
| Name | Description |
|---|---|
| $ | Acts as a placeholder to update the first element that matches the query condition in an update. |
| $addToSet | Adds elements to an array only if they do not already exist in the set. |
| $pop | Removes the first or last item of an array. |
| $pullAll | Removes all matching values from an array. |
| $pull | Removes all array elements that match a specified query. |
| $pushAll | Deprecated. Adds several items to an array. |
| $push | Adds an item to an array. |
Modifiers¶
| Name | Description |
|---|---|
| $each | Modifies the $push and $addToSet operators to append multiple items for array updates. |
| $slice | Modifies the $push operator to limit the size of updated arrays. |
| $sort | Modifies the $push operator to reorder documents stored in an array. |
| $position | Modifies the $push operator to specify the position in the array to add elements. |