docs/content/append-table/update.md

---
title: "Update"
weight: 4
type: docs
aliases:
- /append-table/update.html
---
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# Update

Now, only Spark SQL supports DELETE & UPDATE, you can take a look at [Spark Write]({{< ref "spark/sql-write" >}}).

Example:
```sql
DELETE FROM my_table WHERE currency = 'UNKNOWN';
```

Update append table has two modes:

1. COW (Copy on Write): search for the hit files and then rewrite each file to remove the data that needs to be deleted
   from the files. This operation is costly.
2. MOW (Merge on Write): By specifying `'deletion-vectors.enabled' = 'true'`, the Deletion Vectors mode can be enabled.
   Only marks certain records of the corresponding file for deletion and writes the deletion file, without rewriting the entire file.