> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/sql-functions/special-functions/json-functions/json_merge_preserve.md).

# JSON\_MERGE\_PRESERVE

## Syntax

```bnf
JSON_MERGE_PRESERVE(json_doc, json_doc[, json_doc] ...)
```

## Description

Merges the given JSON documents, returning the merged result, or `NULL` if any argument is `NULL`.

`JSON_MERGE_PRESERVE` is a synonym for [JSON\_MERGE](/docs/server/reference/sql-functions/special-functions/json-functions/json_merge.md), which has been deprecated.

Unlike [JSON\_MERGE\_PATCH](/docs/server/reference/sql-functions/special-functions/json-functions/json_merge_patch.md), members with duplicate keys are preserved.

## Example

```sql
SET @json1 = '[1, 2]';
SET @json2 = '[2, 3]';
SELECT JSON_MERGE_PATCH(@json1,@json2),JSON_MERGE_PRESERVE(@json1,@json2);
+---------------------------------+------------------------------------+
| JSON_MERGE_PATCH(@json1,@json2) | JSON_MERGE_PRESERVE(@json1,@json2) |
+---------------------------------+------------------------------------+
| [2, 3]                          | [1, 2, 2, 3]                       |
+---------------------------------+------------------------------------+
```

## See Also

* [JSON\_MERGE\_PATCH](/docs/server/reference/sql-functions/special-functions/json-functions/json_merge_patch.md)

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