> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kinetica.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Schemas

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<a id="collections" />

<a id="schema" />

<a id="schemas" />

A *schema* is a container for all database objects, providing namespacing for
them.

Namespacing occurs at the schema level and at the category level, meaning that:

* One *schema* could contain a *table* with the same name as a *table* in
  another *schema*.
* One *schema* could contain a *data source* and *data sink* with the same name.
* One *schema* cannot contain an *external table* and a *view* with the same
  name.

Each object in the database will have a containing *schema*; no object will
exist outside of all *schemas*.

## Name Resolution

A database object within a specific *schema* can be addressed by
*qualified name*, prefixing the *object* name with the *schema* name separated
by a dot; e.g.:

```
<schema name>.<object name>
```

Database objects referenced without a *qualified name* will be looked for in the
user's [default schema](/content/concepts/schemas#schema-default), if assigned.

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## Naming Criteria

Each *schema* is identified by a name, which must meet the following criteria:

* Between 1 and 200 characters long
* Alphanumeric, including spaces and these symbols: `_` `{` `}` `[`
  `]` `:` `-` `(` `)` `#`
* First character is alphanumeric or an underscore
* Unique among *schemas*--cannot have the same name as another *schema*, but can
  have the same name as any other database object

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## Visibility

A *schema* will be visible to any user in any of the following situations:

* The user has `system_admin`, `system_read`, or `system_write` permission
* The user has `table_admin` or `table_read` permission on the *schema*
* The user has `table_admin` or `table_read` permission on at least one
  *table* or *view* within the *schema*

The [home schema](/content/concepts/schemas#schema-home) will always be visible to all users.

<a id="schema-default" />

## Default Schema

A *default schema* can be associated with any user, to apply a default
containing *schema* to any *table* or other object references that a user makes
when the user does not specify a *schema* explicitly.

When creating a *table* or other object, including the result table of any
operation, without specifying the *schema*, that object will be created in the
user's *default schema*.  If the user has no *default schema*, an error will be
returned.

When attempting to perform an operation on an existing *table* or other object
(reading, writing, altering, etc.) without specifying a *schema*, the object
will be looked for in the user's *default schema*.  If it is not found
there, or if the user has no *default schema*, an error will be returned.

A user can be assigned a *default schema* during creation, using the
[/create/user/internal](/content/api/rest/create_user_internal_rest) endpoint, or after creation, using the
[/alter/user](/content/api/rest/alter_user_rest) endpoint.

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## Home Schema

Upgrades from releases of *Kinetica* prior to version *7.1* will have a
*home schema* named `ki_home`.

Any top-level tables (those not contained within a *schema*) that existed prior
to the upgrade will be moved to the *home schema* during the upgrade.

Any users that existed prior to the upgrade will be given the *home schema* as
their *default schema*, so that any unqualified references to those top-tables
in existing applications will continue to function without modification.  All
new users will have the *home schema* as their *default schema* by default as
well, for consistency.

## Built-in Schemas

In addition to the [home schema](/content/concepts/schemas#schema-home), there are several
*schemas* that may exist in a default *Kinetica* installation.

| Schema         | Description                                                                                                                                            |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `demo`         | Contains any [demo datasets](/content/admin/gadmin/cluster#cluster-demo) loaded into the database.                                                     |
| `ki_home`      | The *Kinetica* [home schema](/content/concepts/schemas#schema-home), and the [default schema](/content/concepts/schemas#schema-default) for all users. |
| `sys_security` | Contains temporary tables created during row/column security processing. <br /> <Info> Only visible to users with `sys_admin` permission. </Info>      |
| `sys_sql_temp` | Contains temporary tables created during the execution of SQL queries. <br /> <Info> Only visible to users with `sys_admin` permission. </Info>        |
| `sys_temp`     | Contains temporary tables created in processing user requests. <br /> <Info> Only visible to users with `sys_admin` permission. </Info>                |
| `SYSTEM`       | Contains the [ITER](/content/sql/query#sql-iteration) virtual table.                                                                                   |

## Schema Management

*Schemas* have the same naming criteria as [tables](/content/concepts/tables#table), and cannot be
named any of the following, regardless of case:

* `KINETICA`
* `PUBLIC`
* `ROOT`
* `SYSTEM`

A *schema* can be created using the [/create/schema](/content/api/rest/create_schema_rest) endpoint.

After a *schema* is created, *tables* and other objects can be added to the
*schema* at creation time using any endpoints that create them, prefixing the
name of the object to create with the *schema* name, separated by a dot.

A *schema* can be dropped using the [/drop/schema](/content/api/rest/drop_schema_rest) endpoint.