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‎docs/en/guides/56-security/recovery-from-operational-errors.md‎

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---
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title: Recovery from Operational Errors
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---
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import IndexOverviewList from '@site/src/components/IndexOverviewList';
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# Recovery from Operational Errors
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This guide provides step-by-step instructions for recovering from common operational errors in Databend.
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## Introduction
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Databend can help you recover from these common operational errors:
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- **Accidentally dropped databases**
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- **Accidentally dropped tables**
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- **Incorrect data modifications (UPDATE/DELETE operations)**
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- **Accidentally truncated tables**
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- **Data loading mistakes**
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- **Schema evolution rollbacks** (reverting table structure changes)
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- **Dropped columns or constraints**
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These recovery capabilities are powered by Databend's FUSE engine with its Git-like storage design, which maintains snapshots of your data at different points in time.
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## Recovery Scenarios and Solutions
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### Scenario: Accidentally Dropped Database
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If you've accidentally dropped a database, you can restore it using the `UNDROP DATABASE` command:
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1. Identify the dropped database:
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```sql
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SHOW DROP DATABASES LIKE '%sales_data%';
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```
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2. Restore the dropped database:
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```sql
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UNDROP DATABASE sales_data;
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```
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3. Verify the database has been restored:
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```sql
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SHOW DATABASES;
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```
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4. Restore ownership (if needed):
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```sql
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GRANT OWNERSHIP on sales_data.* to ROLE <role_name>;
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```
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**Important**: A dropped database can only be restored within the retention period (default is 24 hours).
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For more details, see [UNDROP DATABASE](/sql/sql-commands/ddl/database/undrop-database) and [SHOW DROP DATABASES](/sql/sql-commands/ddl/database/show-drop-databases).
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### Scenario: Accidentally Dropped Table
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If you've accidentally dropped a table, you can restore it using the `UNDROP TABLE` command:
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1. Identify the dropped table:
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```sql
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SHOW DROP TABLES LIKE '%order%';
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```
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2. Restore the dropped table:
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```sql
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UNDROP TABLE sales_data.orders;
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```
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3. Verify the table has been restored:
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```sql
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SHOW TABLES FROM sales_data;
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```
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4. Restore ownership (if needed):
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```sql
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GRANT OWNERSHIP on sales_data.orders to ROLE <role_name>;
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```
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**Important**: A dropped table can only be restored within the retention period (default is 24 hours).
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For more details, see [UNDROP TABLE](/sql/sql-commands/ddl/table/ddl-undrop-table) and [SHOW DROP TABLES](/sql/sql-commands/ddl/table/show-drop-tables).
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### Scenario: Incorrect Data Updates or Deletions
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If you've accidentally modified or deleted data in a table, you can restore it to a previous state using the `FLASHBACK TABLE` command:
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1. Identify the snapshot ID or timestamp before the incorrect operation:
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```sql
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SELECT * FROM fuse_snapshot('sales_data', 'orders');
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```
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```text
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snapshot_id: c5c538d6b8bc42f483eefbddd000af7d
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snapshot_location: 29356/44446/_ss/c5c538d6b8bc42f483eefbddd000af7d_v2.json
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format_version: 2
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previous_snapshot_id: NULL
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[... ...]
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timestamp: 2023-04-19 04:20:25.062854
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```
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2. Restore the table to the previous state:
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```sql
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-- Using snapshot ID
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ALTER TABLE sales_data.orders FLASHBACK TO (SNAPSHOT => 'c5c538d6b8bc42f483eefbddd000af7d');
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-- Or using timestamp
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ALTER TABLE sales_data.orders FLASHBACK TO (TIMESTAMP => '2023-04-19 04:20:25.062854'::TIMESTAMP);
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```
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3. Verify the data has been restored:
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```sql
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SELECT * FROM sales_data.orders LIMIT 3;
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```
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**Important**: Flashback operations are only possible for existing tables and within the retention period.
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For more details, see [FLASHBACK TABLE](/sql/sql-commands/ddl/table/flashback-table).
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### Scenario: Schema Evolution Rollbacks
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If you've made unwanted changes to a table's structure, you can revert to the previous schema:
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1. Create a table and add some data:
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```sql
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CREATE OR REPLACE TABLE customers (id INT, name VARCHAR, email VARCHAR);
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INSERT INTO customers VALUES (1, 'John', '[email protected]');
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```
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2. Make schema changes:
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```sql
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ALTER TABLE customers ADD COLUMN phone VARCHAR;
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DESC customers;
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```
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Output:
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```text
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┌─────────┬─────────┬──────┬─────────┬─────────┐
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│ Field │ Type │ Null │ Default │ Extra │
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├─────────┼─────────┼──────┼─────────┼─────────┤
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│ id │ INT │ YES │ NULL │ │
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│ name │ VARCHAR │ YES │ NULL │ │
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│ email │ VARCHAR │ YES │ NULL │ │
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│ phone │ VARCHAR │ YES │ NULL │ │
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└─────────┴─────────┴──────┴─────────┴─────────┘
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```
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3. Find the snapshot ID from before the schema change:
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```sql
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SELECT * FROM fuse_snapshot('default', 'customers');
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```
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Output:
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```text
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snapshot_id: 01963cefafbb785ea393501d2e84a425 timestamp: 2025-04-16 04:51:03.227000 previous_snapshot_id: 01963ce9cc29735b87886a08d3ca7e2f
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snapshot_id: 01963ce9cc29735b87886a08d3ca7e2f timestamp: 2025-04-16 04:44:37.289000 previous_snapshot_id: NULL
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```
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4. Revert to the previous schema (using the earlier snapshot):
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```sql
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ALTER TABLE customers FLASHBACK TO (SNAPSHOT => '01963ce9cc29735b87886a08d3ca7e2f');
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```
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5. Verify the schema has been restored:
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```sql
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DESC customers;
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```
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Output:
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```text
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┌─────────┬─────────┬──────┬─────────┬─────────┐
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│ Field │ Type │ Null │ Default │ Extra │
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├─────────┼─────────┼──────┼─────────┼─────────┤
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│ id │ INT │ YES │ NULL │ │
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│ name │ VARCHAR │ YES │ NULL │ │
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│ email │ VARCHAR │ YES │ NULL │ │
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└─────────┴─────────┴──────┴─────────┴─────────┘
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```
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## Important Considerations and Limitations
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- **Time Constraints**: Recovery only works within the retention period (default: 24 hours).
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- **Name Conflicts**: Cannot undrop if an object with the same name exists — [rename database](/sql/sql-commands/ddl/database/ddl-alter-database) or [rename table](/sql/sql-commands/ddl/table/ddl-rename-table) first.
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- **Ownership**: Ownership isn't automatically restored—manually grant it after recovery.
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- **Transient Tables**: Flashback doesn't work for transient tables (no snapshots stored).
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**For Emergency Situations**: Facing critical data loss? Contact Databend Support immediately for help.
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[Contact Databend Support](https://www.databend.com/contact-us/)

‎docs/en/sql-reference/10-sql-commands/00-ddl/00-database/undrop-database.md‎

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Restores the most recent version of a dropped database. This leverages the Databend Time Travel feature; a dropped object can be restored only within a retention period (defaults to 24 hours).
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See also: [DROP DATABASE](ddl-drop-database.md)
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**See also:**
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[DROP DATABASE](ddl-drop-database.md)
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[SHOW DROP DATABASES](show-drop-databases.md)
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## Syntax
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‎docs/en/sql-reference/10-sql-commands/00-ddl/01-table/21-ddl-undrop-table.md‎

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- [CREATE TABLE](./10-ddl-create-table.md)
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- [DROP TABLE](./20-ddl-drop-table.md)
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- [SHOW TABLES](show-tables.md)
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- [SHOW DROP TABLES](show-drop-tables.md)
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## Syntax
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