ClickHouse/docs/en/query_language/show.md

95 lines
2.8 KiB
Markdown
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

# SHOW Queries
## SHOW CREATE TABLE
```sql
SHOW CREATE [TEMPORARY] [TABLE|DICTIONARY] [db.]table [INTO OUTFILE filename] [FORMAT format]
```
Returns a single `String`-type 'statement' column, which contains a single value the `CREATE` query used for creating the specified object.
## SHOW DATABASES {#show-databases}
```sql
SHOW DATABASES [INTO OUTFILE filename] [FORMAT format]
```
Prints a list of all databases.
This query is identical to `SELECT name FROM system.databases [INTO OUTFILE filename] [FORMAT format]`.
## SHOW PROCESSLIST
```sql
SHOW PROCESSLIST [INTO OUTFILE filename] [FORMAT format]
```
Outputs the content of the [system.processes](../operations/system_tables.md#system_tables-processes) table, that contains a list of queries that is being processed at the moment, excepting `SHOW PROCESSLIST` queries.
The `SELECT * FROM system.processes` query returns data about all the current queries.
Tip (execute in the console):
```bash
$ watch -n1 "clickhouse-client --query='SHOW PROCESSLIST'"
```
## SHOW TABLES
Displays a list of tables.
```sql
SHOW [TEMPORARY] TABLES [FROM <db>] [LIKE '<pattern>'] [LIMIT <N>] [INTO OUTFILE <filename>] [FORMAT <format>]
```
If the `FROM` clause is not specified, the query returns the list of tables from the current database.
You can get the same results as the `SHOW TABLES` query in the following way:
```sql
SELECT name FROM system.tables WHERE database = <db> [AND name LIKE <pattern>] [LIMIT <N>] [INTO OUTFILE <filename>] [FORMAT <format>]
```
**Example**
The following query selects the first two rows from the list of tables in the `system` database, whose names contain `co`.
```sql
SHOW TABLES FROM system LIKE '%co%' LIMIT 2
```
```text
┌─name───────────────────────────┐
│ aggregate_function_combinators │
│ collations │
└────────────────────────────────┘
```
## SHOW DICTIONARIES
Displays a list of [external dictionaries](dicts/external_dicts.md).
```sql
SHOW DICTIONARIES [FROM <db>] [LIKE '<pattern>'] [LIMIT <N>] [INTO OUTFILE <filename>] [FORMAT <format>]
```
If the `FROM` clause is not specified, the query returns the list of dictionaries from the current database.
You can get the same results as the `SHOW DICTIONARIES` query in the following way:
```sql
SELECT name FROM system.dictionaries WHERE database = <db> [AND name LIKE <pattern>] [LIMIT <N>] [INTO OUTFILE <filename>] [FORMAT <format>]
```
**Example**
The following query selects the first two rows from the list of tables in the `system` database, whose names contain `co`.
```sql
SHOW DICTIONARIES FROM db LIKE '%reg%' LIMIT 2
```
```text
┌─name─────────┐
│ regions │
│ region_names │
└──────────────┘
```