---
title: UPDATE
slug: dql/update
docTags: 
createdAt: 2023-11-02T21:43:20.895Z
---

The <font color="#db2777">`UPDATE`</font> operation modifies the content of existing documents in a collection. With an <font color="#db2777">`UPDATE`</font> statement, you can update specific fields within the documents based on specified conditions:

:::CodeblockTabs
DQL

```sql
UPDATE your_collection_name
SET field1 = value1, field2 -> [mutator], ...
WHERE [condition]
```
:::

In this syntax:

- `your_collection_name` is the name of the collection in which you want to update data.
- `field1 = value1, field2 -> [mutator], ...` represents the fields to be updated and their corresponding new value or functional mutator.
- `[condition]` is the expression or set of conditions that determine which documents should be included in the result set.

# Basic UPDATE

Here is an example of a basic <font color="#db2777">`UPDATE`</font> operation:

:::CodeblockTabs
DQL

```sql
UPDATE your_collection_name
SET field1 = 'blue'
WHERE _id = '123'
```
:::

# UPDATE Multiple Fields

The following snippet shows an example<font color="#db2777">`UPDATE`</font> setting multiple fields:

:::CodeblockTabs
DQL

```sql
UPDATE your_collection_name
SET
  field1 = 'blue',
  field2 = 0
WHERE _id = '123'
```
:::

# UPDATE with MAP Type

When updating fields nested in a `MAP`, specify the field-value pairs you want to update.

:::hint{type="info"}
For `MAP` syntax, see Ditto Query Language > Types and Definitions > [Map Operations](docId:4f33y__UQ6CBwFsm0h7aq).
:::

:::CodeblockTabs
DQL

```sql
UPDATE COLLECTION your_collection_name (field2 MAP)
SET
  field2 -> (
     sub1 = 2,
     sub2 = 'spring'
  )
WHERE field1 = 'red'
```
:::

# Flagging Fields as Removed&#x20;

In DQL, you can mark a field as a *tombstone*. A tombstone is a flag signaling to remote peers that the field is deleted from the local Ditto store.&#x20;

:::hint{type="info"}
In Ditto, when performing an operation like an <font color="#db2777">`UPDATE`</font>, excluding fields from your payload does *not* remove the existing data from the system. In other words, Ditto ignores any fields you've omitted from your payload and therefore they remain unchanged by that particular operation.
:::

To set a field as a tombstone, use the syntax `[field] -> tombstone()` as follows:

:::CodeblockTabs
DQL

```sql
UPDATE your_collection_name
SET your_field_name -> tombstone()
WHERE _id = '123'
```
:::

## Setting a MAP as a Tombstone

Using the `tombstone()` functional operation, you can mark a `MAP` data type as deleted.&#x20;

When a `MAP` is tombstoned, a metadata property is internally set on the field and all the data within the `MAP` is removed. This is done by iterating through all the fields in the `MAP` and calling `tombstone` on those fields.&#x20;

For `REGISTER` and `ATTACHMENT` data types within the `MAP`,  flagging values with `tombstone` results in their deletion.

:::CodeblockTabs
DQL

```sql
UPDATE COLLECTION cars (properties MAP)
SET
  properties -> tombstone()
WHERE
  _id = '123' 
```
:::

For more information and how-to instructions, see [Ditto Query Language](docId\:l4GTGDVu5F3wRnUHYLvUT) > [Types and Definitions](docId\:Ht6klTeCy3iZO8JO34Ga3) > [Tombstone Operation](docId\:Ht6klTeCy3iZO8JO34Ga3).