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Docs: Update information_schema with case-insensitity

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Robert Schulze 2023-09-12 18:07:46 +00:00
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docs/en/operations/system-tables/information_schema.md
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@ -3,12 +3,13 @@ slug: /en/operations/system-tables/information_schema
---
# INFORMATION_SCHEMA
`INFORMATION_SCHEMA` (`information_schema`) is a system database that contains views. Using these views, you can get information about the metadata of database objects. These views read data from the columns of the [system.columns](../../operations/system-tables/columns.md), [system.databases](../../operations/system-tables/databases.md) and [system.tables](../../operations/system-tables/tables.md) system tables.
The structure and composition of system tables may change in different versions of the product, but the support of the `information_schema` makes it possible to change the structure of system tables without changing the method of access to metadata. Metadata requests do not depend on the DBMS used.
`INFORMATION_SCHEMA` (or: `information_schema`) is a system database which provides a (somewhat) standardized, [DBMS-agnostic view](https://en.wikipedia.org/wiki/Information_schema) on metadata of database objects. The views in `INFORMATION_SCHEMA` are generally inferior to normal system tables but tools can use them to obtain basic information in a cross-DBMS manner. The structure and content of views in `INFORMATION_SCHEMA` is supposed to evolves in a backwards-compatible way, i.e. only new functionality is added but existing functionality is not changed or removed. In terms of internal implementation, views in `INFORMATION_SCHEMA` usually map to to normal systme tables like [system.columns](../../operations/system-tables/columns.md), [system.databases](../../operations/system-tables/databases.md) and [system.tables](../../operations/system-tables/tables.md).
``` sql
SHOW TABLES FROM INFORMATION_SCHEMA;
-- or:
SHOW TABLES FROM information_schema;
```
``` text
@ -17,6 +18,10 @@ SHOW TABLES FROM INFORMATION_SCHEMA;
│ SCHEMATA │
│ TABLES │
│ VIEWS │
│ columns │
│ schemata │
│ tables │
│ views │
└──────────┘
```
@ -27,6 +32,8 @@ SHOW TABLES FROM INFORMATION_SCHEMA;
- [TABLES](#tables)
- [VIEWS](#views)
Case-insensitive equivalent views, e.g. `INFORMATION_SCHEMA.columns` are provided for reasons of compatibility with other databases.
## COLUMNS {#columns}
Contains columns read from the [system.columns](../../operations/system-tables/columns.md) system table and columns that are not supported in ClickHouse or do not make sense (always `NULL`), but must be by the standard.