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<!--Shortcode-->
{{% product-name %}} stores data related to the database server, queries, and tables in _system tables_.
You can query the system tables for information about your running server, databases, and and table schemas.
## Query system tables
- [Use the HTTP query API](#use-the-http-query-api)
- [Examples](#examples)
- [Show tables](#show-tables)
- [View column information for a table](#view-column-information-for-a-table)
### Use the HTTP query API
Use the HTTP API `/api/v3/query_sql` endpoint to retrieve system information about your database server and table schemas in {{% product-name %}}.
To execute a query, send a `GET` or `POST` request to the endpoint:
- `GET`: Pass parameters in the URL query string (for simple queries)
- `POST`: Pass parameters in a JSON object (for complex queries and readability in your code)
Include the following parameters:
- `q`: _({{< req >}})_ The SQL query to execute.
- `db`: _({{< req >}})_ The database to execute the query against.
- `params`: A JSON object containing parameters to be used in a _parameterized query_.
- `format`: The format of the response (`json`, `jsonl`, `csv`, `pretty`, or `parquet`).
JSONL (`jsonl`) is preferred because it streams results back to the client.
`pretty` is for human-readable output. Default is `json`.
#### Examples
> [!Note]
> #### system\_ sample data
>
> In examples, tables with `"table_name":"system_` are user-created tables for CPU, memory, disk,
> network, and other resource statistics collected and written
> by the user--for example, using the `psutil` Python library or
> [Telegraf](/telegraf/v1/get-started/) to collect
> and write system metrics to an InfluxDB 3 database.
##### Show tables
The following example sends a `GET` request that executes a `show tables` query
to retrieve all user-created
tables (`"table_schema":"iox"`), system tables, and information schema tables
for a database:
```bash
curl "http://{{< influxdb/host >}}/api/v3/query_sql?db=mydb&format=jsonl&q=show%20tables"
```
The response body contains the following JSONL:
```jsonl
{"table_catalog":"public","table_schema":"iox","table_name":"system_cpu","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_cpu_cores","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_memory","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_memory_faults","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_disk_usage","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_disk_io","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_disk_performance","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_network","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"distinct_caches","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"last_caches","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"parquet_files","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"processing_engine_plugins","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"processing_engine_triggers","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"system","table_name":"queries","table_type":"BASE TABLE"}
{"table_catalog":"public","table_schema":"information_schema","table_name":"tables","table_type":"VIEW"}
{"table_catalog":"public","table_schema":"information_schema","table_name":"views","table_type":"VIEW"}
{"table_catalog":"public","table_schema":"information_schema","table_name":"columns","table_type":"VIEW"}
{"table_catalog":"public","table_schema":"information_schema","table_name":"df_settings","table_type":"VIEW"}
{"table_catalog":"public","table_schema":"information_schema","table_name":"schemata","table_type":"VIEW"}
```
A table has one of the following `table_schema` values:
- `iox`: tables created by the user of the database.
- `system`: tables used by the system to show information about the running database server.
Some of these tables show stored information such as configurations,
while others, such as the `queries` table, hold ephemeral state in memory.
- `information_schema`: views that show schema information for tables in the database.
#### View column information for a table
The following query sends a `POST` request that executes an SQL query to
retrieve information about columns in the sample `system_swap` table schema:
_Note: when you send a query in JSON, you must escape single quotes
that surround field names._
```bash
curl "http://localhost:8181/api/v3/query_sql" \
--header "Content-Type: application/json" \
--json '{
"db": "mydb",
"q": "SELECT * FROM information_schema.columns WHERE table_schema = '"'iox'"' AND table_name = '"'system_swap'"'",
"format": "jsonl"
}'
```
The output is the following:
```jsonl
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"free","ordinal_position":0,"is_nullable":"YES","data_type":"UInt64"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"host","ordinal_position":1,"is_nullable":"NO","data_type":"Dictionary(Int32, Utf8)"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"percent","ordinal_position":2,"is_nullable":"YES","data_type":"Float64","numeric_precision":24,"numeric_precision_radix":2}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"sin","ordinal_position":3,"is_nullable":"YES","data_type":"UInt64"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"sout","ordinal_position":4,"is_nullable":"YES","data_type":"UInt64"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"time","ordinal_position":5,"is_nullable":"NO","data_type":"Timestamp(Nanosecond, None)"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"total","ordinal_position":6,"is_nullable":"YES","data_type":"UInt64"}
{"table_catalog":"public","table_schema":"iox","table_name":"system_swap","column_name":"used","ordinal_position":7,"is_nullable":"YES","data_type":"UInt64"}
```
#### Recently executed queries
To view recently executed queries, query the `queries` system table:
```bash
curl "http://localhost:8181/api/v3/query_sql" \
--header "Content-Type: application/json" \
--json '{
"db": "mydb",
"q": "SELECT * FROM system.queries LIMIT 2",
"format": "jsonl"
}'
```
The output is similar to the following:
```jsonl
{"id":"cdd63409-1822-4e65-8e3a-d274d553dbb3","phase":"success","issue_time":"2025-01-20T17:01:40.690067","query_type":"sql","query_text":"show tables","partitions":0,"parquet_files":0,"plan_duration":"PT0.032689S","permit_duration":"PT0.000202S","execute_duration":"PT0.000223S","end2end_duration":"PT0.033115S","compute_duration":"P0D","max_memory":0,"success":true,"running":false,"cancelled":false}
{"id":"47f8d312-5e75-4db2-837a-6fcf94c09927","phase":"success","issue_time":"2025-01-20T17:02:32.627782","query_type":"sql","query_text":"show tables","partitions":0,"parquet_files":0,"plan_duration":"PT0.000583S","permit_duration":"PT0.000015S","execute_duration":"PT0.000063S","end2end_duration":"PT0.000662S","compute_duration":"P0D","max_memory":0,"success":true,"running":false,"cancelled":false}
```
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