> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-3a82795f.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
> Documentation for Table Functions
# Table Functions
Table functions are methods for constructing tables.
| Page | Description |
| ----------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| [azureBlobStorage](/reference/functions/table-functions/azureBlobStorage) | Provides a table-like interface to select/insert files in Azure Blob Storage. Similar to the s3 function. |
| [azureBlobStorageCluster](/reference/functions/table-functions/azureBlobStorageCluster) | Allows processing files from Azure Blob storage in parallel with many nodes in a specified cluster. |
| [clusterAllReplicas](/reference/functions/table-functions/cluster) | Allows accessing all shards (configured in the `remote_servers` section) of a cluster without creating a Distributed table. |
| [deltaLake](/reference/functions/table-functions/deltalake) | Provides a read-only table-like interface to the Delta Lake tables in Amazon S3. |
| [deltaLakeCluster](/reference/functions/table-functions/deltalakeCluster) | This is an extension to the deltaLake table function. |
| [dictionary](/reference/functions/table-functions/dictionary) | Displays the dictionary data as a ClickHouse table. Works the same way as the Dictionary engine. |
| [executable](/reference/functions/table-functions/executable) | The `executable` table function creates a table based on the output of a user-defined function (UDF) that you define in a script that outputs rows to **stdout**. |
| [file](/reference/functions/table-functions/file) | A table engine which provides a table-like interface to SELECT from and INSERT into files, similar to the s3 table function. Use `file()` when working with local files, and `s3()` when working with buckets in object storage such as S3, GCS, or MinIO. |
| [fileCluster](/reference/functions/table-functions/fileCluster) | Enables simultaneous processing of files matching a specified path across multiple nodes within a cluster. The initiator establishes connections to worker nodes, expands globs in the file path, and delegates file-reading tasks to worker nodes. Each worker node is querying the initiator for the next file to process, repeating until all tasks are completed (all files are read). |
| [filesystem](/reference/functions/table-functions/filesystem) | Provides access to the file system to list files and return their metadata and contents. |
| [format](/reference/functions/table-functions/format) | Parses data from arguments according to specified input format. If structure argument is not specified, it's extracted from the data. |
| [gcs](/reference/functions/table-functions/gcs) | Provides a table-like interface to `SELECT` and `INSERT` data from Google Cloud Storage. Requires the `Storage Object User` IAM role. |
| [fuzzQuery](/reference/functions/table-functions/fuzzQuery) | Perturbs the given query string with random variations. |
| [fuzzJSON](/reference/functions/table-functions/fuzzJSON) | Perturbs a JSON string with random variations. |
| [generateRandom](/reference/functions/table-functions/generate) | Generates random data with a given schema. Allows populating test tables with that data. Not all types are supported. |
| [mergeTreeTextIndex](/reference/functions/table-functions/mergeTreeTextIndex) | Represents the dictionary of a text index in a MergeTree table. It can be used for introspection. |
| [mergeTreeProjection](/reference/functions/table-functions/mergeTreeProjection) | Represents the contents of some projection in MergeTree tables. It can be used for introspection. |
| [mergeTreeIndex](/reference/functions/table-functions/mergeTreeIndex) | Represents the contents of index and marks files of MergeTree tables. It can be used for introspection. |
| [hdfs](/reference/functions/table-functions/hdfs) | Creates a table from files in HDFS. This table function is similar to the url and file table functions. |
| [hdfsCluster](/reference/functions/table-functions/hdfsCluster) | Allows processing files from HDFS in parallel from many nodes in a specified cluster. |
| [hudi](/reference/functions/table-functions/hudi) | Provides a read-only table-like interface to Apache Hudi tables in Amazon S3. |
| [ytsaurus](/reference/functions/table-functions/ytsaurus) | The table function allows to read data from the YTsaurus cluster. |
| [hudiCluster Table Function](/reference/functions/table-functions/hudiCluster) | An extension to the hudi table function. Allows processing files from Apache Hudi tables in Amazon S3 in parallel with many nodes in a specified cluster. |
| [iceberg](/reference/functions/table-functions/iceberg) | Provides a read-only table-like interface to Apache Iceberg tables in Amazon S3, Azure, HDFS or locally stored. |
| [paimon](/reference/functions/table-functions/paimon) | Provides a read-only table-like interface to Apache Paimon tables in Amazon S3, Azure, HDFS or locally stored. |
| [icebergCluster](/reference/functions/table-functions/icebergCluster) | An extension to the iceberg table function which allows processing files from Apache Iceberg in parallel from many nodes in a specified cluster. |
| [paimonCluster](/reference/functions/table-functions/paimonCluster) | An extension to the paimon table function which allows processing files from Apache Paimon in parallel from many nodes in a specified cluster. |
| [input](/reference/functions/table-functions/input) | Table function that allows effectively converting and inserting data sent to the server with a given structure to a table with another structure. |
| [jdbc](/reference/functions/table-functions/jdbc) | Returns a table that is connected via JDBC driver. |
| [merge](/reference/functions/table-functions/merge) | Creates a temporary Merge table. The structure will be derived from underlying tables by using a union of their columns and by deriving common types. |
| [mongodb](/reference/functions/table-functions/mongodb) | Allows `SELECT` queries to be performed on data that is stored on a remote MongoDB server. |
| [mysql](/reference/functions/table-functions/mysql) | Allows `SELECT` and `INSERT` queries to be performed on data that are stored on a remote MySQL server. |
| [null](/reference/functions/table-functions/null) | Creates a temporary table of the specified structure with the Null table engine. The function is used for the convenience of test writing and demonstrations. |
| [timeSeriesMetrics](/reference/functions/table-functions/timeSeriesMetrics) | timeSeriesMetrics returns the metrics table used by table `db_name.time_series_table` whose table engine is the TimeSeries engine. |
| [timeSeriesSelector](/reference/functions/table-functions/timeSeriesSelector) | Reads time series from a TimeSeries table filtered by a selector and with timestamps in a specified interval. |
| [timeSeriesTags](/reference/functions/table-functions/timeSeriesTags) | timeSeriesTags table function returns the tags table use by table `db_name.time_series_table` whose table engine is the TimeSeries engine. |
| [prometheusQueryRange](/reference/functions/table-functions/prometheusQueryRange) | Evaluates a prometheus query using data from a TimeSeries table. |
| [zeros](/reference/functions/table-functions/zeros) | Used for test purposes as the fastest method to generate many rows. Similar to the `system.zeros` and `system.zeros_mt` system tables. |
| [primes](/reference/functions/table-functions/primes) | Returns a table with a single `prime` column that contains prime numbers. |
| [timeSeriesData](/reference/functions/table-functions/timeSeriesData) | timeSeriesData returns the data table used by table `db_name.time_series_table` whose table engine is TimeSeries. |
| [numbers](/reference/functions/table-functions/numbers) | Returns a table with a single `number` column that contains a sequence of integers. |
| [prometheusQuery](/reference/functions/table-functions/prometheusQuery) | Evaluates a prometheus query using data from a TimeSeries table. |
| [generate\_series (generateSeries)](/reference/functions/table-functions/generate_series) | Returns a table with the single `generate_series` column (UInt64) that contains integers from start to stop inclusively. |
| [odbc](/reference/functions/table-functions/odbc) | Returns the table that is connected via ODBC. |
| [postgresql](/reference/functions/table-functions/postgresql) | Allows `SELECT` and `INSERT` queries to be performed on data that is stored on a remote PostgreSQL server. |
| [redis](/reference/functions/table-functions/redis) | This table function allows integrating ClickHouse with Redis. |
| [remote, remoteSecure](/reference/functions/table-functions/remote) | Table function `remote` allows to access remote servers on-the-fly, i.e. without creating a distributed table. Table function `remoteSecure` is same as `remote` but over a secure connection. |
| [s3 Table Function](/reference/functions/table-functions/s3) | Provides a table-like interface to select/insert files in Amazon S3 and Google Cloud Storage. This table function is similar to the hdfs function, but provides S3-specific features. |
| [s3Cluster](/reference/functions/table-functions/s3Cluster) | An extension to the s3 table function, which allows processing files from Amazon S3 and Google Cloud Storage in parallel with many nodes in a specified cluster. |
| [sqlite](/reference/functions/table-functions/sqlite) | Allows to perform queries on data stored in a SQLite database. |
| [arrowFlight](/reference/functions/table-functions/arrowflight) | Allows to perform queries on data exposed via an Apache Arrow Flight server. |
| [url](/reference/functions/table-functions/url) | Creates a table from the `URL` with given `format` and `structure` |
| [urlCluster](/reference/functions/table-functions/urlCluster) | Allows processing files from URL in parallel from many nodes in a specified cluster. |
| [view](/reference/functions/table-functions/view) | Turns a subquery into a table. The function implements views. |
| [values](/reference/functions/table-functions/values) | creates a temporary storage which fills columns with values. |
| [loop](/reference/functions/table-functions/loop) | The loop table function in ClickHouse is used to return query results in an infinite loop. |
Usage
Table functions can be used in the [`FROM`](/reference/statements/select/from)
clause of a `SELECT` query. For example, you can `SELECT` data from a file on your local
machine using the `file` table function.
```bash title="Query" theme={null}
echo "1, 2, 3" > example.csv
```
```text title="Response" theme={null}
./clickhouse client
:) SELECT * FROM file('example.csv')
┌─c1─┬─c2─┬─c3─┐
│ 1 │ 2 │ 3 │
└────┴────┴────┘
```
You can also use table functions for creating a temporary table that is available
only in the current query. For example:
```sql title="Query" theme={null}
SELECT * FROM generateSeries(1,5);
```
```response title="Response" theme={null}
┌─generate_series─┐
│ 1 │
│ 2 │
│ 3 │
│ 4 │
│ 5 │
└─────────────────┘
```
The table is deleted when the query finishes.
Table functions can be used as a way to create tables, using the following syntax:
```sql title="Query" theme={null}
CREATE TABLE [IF NOT EXISTS] [db.]table_name AS table_function()
```
For example:
```sql title="Query" theme={null}
CREATE TABLE series AS generateSeries(1, 5);
SELECT * FROM series;
```
```response title="Response" theme={null}
┌─generate_series─┐
│ 1 │
│ 2 │
│ 3 │
│ 4 │
│ 5 │
└─────────────────┘
```
Finally, table functions can be used to `INSERT` data into a table. For example,
we could write out the contents of the table we created in the previous example
to a file on disk using the `file` table function again:
```sql title="Query" theme={null}
INSERT INTO FUNCTION file('numbers.csv', 'CSV') SELECT * FROM series;
```
```bash title="Query" theme={null}
cat numbers.csv
1
2
3
4
5
```
You can't use table functions if the [allow\_ddl](/reference/settings/session-settings#allow_ddl) setting is disabled.