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60 lines
1.5 KiB
Markdown
60 lines
1.5 KiB
Markdown
---
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toc_priority: 46
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toc_title: GenerateRandom
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---
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# GenerateRandom Table Engine {#table_engines-generate}
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The GenerateRandom table engine produces random data for given table schema.
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Usage examples:
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- Use in test to populate reproducible large table.
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- Generate random input for fuzzing tests.
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## Usage in ClickHouse Server {#usage-in-clickhouse-server}
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``` sql
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ENGINE = GenerateRandom(random_seed, max_string_length, max_array_length)
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```
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The `max_array_length` and `max_string_length` parameters specify maximum length of all
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array columns and strings correspondingly in generated data.
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Generate table engine supports only `SELECT` queries.
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It supports all [DataTypes](../../../sql-reference/data-types/index.md) that can be stored in a table except `LowCardinality` and `AggregateFunction`.
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## Example {#example}
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**1.** Set up the `generate_engine_table` table:
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``` sql
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CREATE TABLE generate_engine_table (name String, value UInt32) ENGINE = GenerateRandom(1, 5, 3)
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```
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**2.** Query the data:
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``` sql
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SELECT * FROM generate_engine_table LIMIT 3
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```
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``` text
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┌─name─┬──────value─┐
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│ c4xJ │ 1412771199 │
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│ r │ 1791099446 │
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│ 7#$ │ 124312908 │
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└──────┴────────────┘
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```
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## Details of Implementation {#details-of-implementation}
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- Not supported:
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- `ALTER`
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- `SELECT ... SAMPLE`
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- `INSERT`
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- Indices
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- Replication
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[Original article](https://clickhouse.tech/docs/en/operations/table_engines/generate/) <!--hide-->
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