Project: ClickHouse (App Definition and Development / Database)
File: remote.md

slug: /en/sql-reference/table-functions/remote sidebar_position: 175 sidebar_label: remote Table function `remote` allows to access remote servers on-the-fly, i.e. without creating a table. Table function `remoteSecure` is same as `remote` but over a secure connection. Both functions can be used in `SELECT` and `INSERT` queries. ``` sql remote(addressesexpr, [db, table, user [, password], shardingkey]) remote(addressesexpr, [db.table, user [, password], shardingkey]) remote(named_collection[, option=value [,..]]) remoteSecure(addressesexpr, [db, table, user [, password], shardingkey]) remoteSecure(addressesexpr, [db.table, user [, password], shardingkey]) remoteSecure(named_collection[, option=value [,..]]) ``` `addresses_expr` A remote server address or an expression that generates multiple addresses of remote servers. Format: `host` or `host:port`. The `host` can be specified as a server name, or as a IPv4 or IPv6 address. An IPv6 address must be specified in square brackets. The `port` is the TCP port on the remote server. If the port is omitted, it uses from the server config file for table function `remote` (by default, 9000) and for table function `remoteSecure` (by default, 9440). For IPv6 addresses, a port is required. If only parameter `addresses_expr` is specified, `db` and `table` will use `system.one` by default. Type: . `db` Database name. Type: . `table` Table name. Type: . `user` User name. If not specified, `default` is used. Type: . `password` User password. If not specified, an empty password is used. Type: . `sharding_key` Sharding key to support distributing data across nodes. For example: `insert into remote('127.0.0.1:9000,127.0.0.2', db, table, 'default', rand())`. Type: . Arguments also can be passed using . A table located on a remote server. As table functions `remote` and `remoteSecure` re-establish the connection for each request, it is recommended to use a `Distributed` table instead. Also, if hostnames are set, the names are resolved, and errors are not counted when working with various replicas. When processing a large number of queries, always create the `Distributed` table ahead of time, and do not use the `remote` table function. The `remote` table function can be useful in the following cases: One-time data migration from one system to another Accessing a specific server for data comparison, debugging, and testing, i.e. ad-hoc connections. Queries between various ClickHouse clusters for research purposes. Infrequent distributed requests that are made manually. Distributed requests where the set of servers is re-defined each time. ``` text example01-01-1 example01-01-1:9440 example01-01-1:9000 localhost 127.0.0.1 ``` Multiple addresses can be comma-separated. In this case, ClickHouse will use distributed processing and send the query to all specified addresses (like shards with different

Example: ``` text example01-01-1,example01-02-1 ``` ``` sql SELECT * FROM remote('127.0.0.1', db.remoteenginetable) LIMIT 3; ``` Or using : ```sql CREATE NAMED COLLECTION creds AS host = '127.0.0.1', database = 'db'; SELECT * FROM remote(creds, table='remoteenginetable') LIMIT 3; ``` ``` sql CREATE TABLE remote_table (name String, value UInt32) ENGINE=Memory; INSERT INTO FUNCTION remote('127.0.0.1', currentDatabase(), 'remote_table') VALUES ('test', 42); SELECT * FROM remote_table; ``` This example uses one table from a sample dataset. The database is `imdb`, and the table is `actors`. Verify the source database and table name (`imdb.actors`) ```sql show databases ``` ```sql show tables in imdb ``` Get the CREATE TABLE statement from the source: ``` select createtablequery from system.tables where database = 'imdb' and table = 'actors' ``` Response ```sql CREATE TABLE imdb.actors (`id` UInt32, `first_name` String, `last_name` String, `gender` FixedString(1)) ENGINE = MergeTree ORDER BY (id, firstname, lastname, gender); ``` Create the destination database: ```sql CREATE DATABASE imdb ``` Using the CREATE TABLE statement from the source, create the destination: ```sql CREATE TABLE imdb.actors (`id` UInt32, `first_name` String, `last_name` String, `gender` FixedString(1)) ENGINE = MergeTree ORDER BY (id, firstname, lastname, gender); ``` Insert into the new database and table created on the remote system. You will need the host, port, username, password, destination database, and destination table. ```sql INSERT INTO FUNCTION remoteSecure('remote.clickhouse.cloud:9440', 'imdb.actors', 'USER', 'PASSWORD') SELECT * from imdb.actors ``` Patterns in curly brackets `{ }` are used to generate a set of shards and to specify replicas. If there are multiple pairs of curly brackets, then the direct product of the corresponding sets is generated. The following pattern types are supported. `{a,b,c}` - Represents any of alternative strings `a`, `b` or `c`. The pattern is replaced with `a` in the first shard address and replaced with `b` in the second shard address and so on. For instance, `example0{1,2}-1` generates addresses `example01-1` and `example02-1`. `{N..M}` - A range of numbers. This pattern generates shard addresses with incrementing indices from `N` to (and including) `M`. For instance, `example0{1..2}-1` generates `example01-1` and `example02-1`. `{0n..0m}` - A range of numbers with leading zeroes. This pattern preserves leading zeroes in indices. For instance, `example{01..03}-1` generates `example01-1`, `example02-1` and `example03-1`. `{a|b}` - Any number of variants separated by a `|`. The pattern specifies replicas. For instance, `example01-{1|2}` generates replicas `example01-1` and `example01-2`. The query will be sent to the first healthy replica. However, for `remote` the replicas are iterated in the order currently set in the setting. The number of generated addresses is limited by setting.