# ALTER SHARE


> Set or clear the include pattern on an existing Share to change which tables and views it exposes.

The `ALTER SHARE` statement changes the include pattern on a Share you own, which controls which tables and views the Share exposes. See [table-level security](/key-tasks/sharing-data/table-level-security/) for the feature overview.

`INCLUDE_PATTERN` is the only option `ALTER SHARE` accepts. To publish new data to a Share, use [`UPDATE SHARE`](update-share.md). To change a Share's access, visibility, or update mode, recreate it with [`CREATE OR REPLACE SHARE`](create-share.md).

:::note
Only the owner of a Share can alter it. Altering a Share owned by another account fails as though the Share doesn't exist.
:::

## Syntax

```sql
ALTER SHARE [ IF EXISTS ] <share name> SET INCLUDE_PATTERN '<pattern list>';
ALTER SHARE [ IF EXISTS ] <share name> RESET INCLUDE_PATTERN;
```

## Parameters

| Parameter | Description |
| --- | --- |
| `<share name>` | The name of a Share you own. Without `IF EXISTS`, a Share that doesn't exist raises an error |
| `IF EXISTS` | Makes the statement a no-op when the Share doesn't exist, for both `SET` and `RESET` |
| `<pattern list>` | A comma-separated list of `schema.table` patterns. See the [`INCLUDE_PATTERN` clause](include-pattern.md) |

`SET` and `RESET` produce three distinct states:

| Statement | Stored value | Effect |
| --- | --- | --- |
| `SET INCLUDE_PATTERN 'reporting.*'` | `[reporting.*]` | The Share exposes what the patterns match |
| `SET INCLUDE_PATTERN ''` | `[]` | The Share exposes nothing. Only the default schema remains |
| `RESET INCLUDE_PATTERN` | `NULL` | The Share exposes the whole database |

Read the stored value back from the `INCLUDE_PATTERN` column of [`LIST SHARES`](list-shares.md) or [`MD_INFORMATION_SCHEMA.OWNED_SHARES`](md_information_schema/owned_shares.md).

`SET INCLUDE_PATTERN` validates every pattern against the source database's **live** catalog, and the check is all-or-nothing: if one pattern in the list matches nothing, the statement fails and the stored pattern is left unchanged. See [validation](include-pattern.md#validation) for the rules that decide whether a pattern matches.

## Propagation

An edit reaches an already-attached consumer on the next update cycle, within a minute or two. Re-attaching the Share picks it up immediately. This includes your own held-open connection, since the owner gets no fast path. The Share URL doesn't change, so an edit never forces consumers to re-attach.

## Example usage

```sql
-- Restrict an existing share to one schema.
ALTER SHARE sales_share SET INCLUDE_PATTERN 'reporting.*';

-- Expose several patterns; they are stored as a list, in order.
ALTER SHARE sales_share SET INCLUDE_PATTERN 'reporting.*, finance.salaries';

-- Expose nothing.
ALTER SHARE sales_share SET INCLUDE_PATTERN '';

-- Go back to exposing the whole database.
ALTER SHARE sales_share RESET INCLUDE_PATTERN;

-- No-op when the share is absent, rather than an error.
ALTER SHARE IF EXISTS maybe_missing RESET INCLUDE_PATTERN;
```

## Troubleshooting

| Error | Cause |
| --- | --- |
| `does not exist` | The Share doesn't exist, or it's owned by another account. Add `IF EXISTS` to make a missing Share a no-op |
| `syntax error` | An option other than `INCLUDE_PATTERN` was given. `ALTER SHARE` accepts no other options |

For errors raised by the pattern itself, such as a pattern that matches nothing or names a missing schema, see [`INCLUDE_PATTERN` errors](include-pattern.md#errors).

## Related

- [Table-level security](/key-tasks/sharing-data/table-level-security/)
- [INCLUDE_PATTERN clause](include-pattern.md)
- [CREATE SHARE](create-share.md)
- [LIST SHARES](list-shares.md)
- [UPDATE SHARE](update-share.md)


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