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51 lines
1.8 KiB
Markdown
51 lines
1.8 KiB
Markdown
---
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slug: /en/operations/system-tables/projections
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---
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# projections
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Contains information about existing projections in all the tables.
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Columns:
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- `database` ([String](../../sql-reference/data-types/string.md)) — Database name.
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- `table` ([String](../../sql-reference/data-types/string.md)) — Table name.
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- `name` ([String](../../sql-reference/data-types/string.md)) — Projection name.
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- `type` ([Enum](../../sql-reference/data-types/enum.md)) — Projection type ('Normal' = 0, 'Aggregate' = 1).
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- `total_rows`, ([UInt64](../../sql-reference/data-types/int-uint.md)) — Total number of rows.
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- `data_compressed_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md)) — The size of compressed data, in bytes.
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- `data_uncompressed_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md)) — The size of decompressed data, in bytes.
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- `sorting_key` ([Array(String)](../../sql-reference/data-types/array.md)) — Projection sorting key.
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- `query` ([String](../../sql-reference/data-types/string.md)) — Projection query.
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**Example**
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```sql
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SELECT * FROM system.projections LIMIT 2 FORMAT Vertical;
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```
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```text
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Row 1:
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──────
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database: default
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table: landing
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name: improved_sorting_key
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type: Normal
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total_rows: 1000
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data_compressed_bytes: 8081
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data_uncompressed_bytes: 12890
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sorting_key: ['user_id','date']
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query: SELECT * ORDER BY user_id, date
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Row 2:
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──────
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database: default
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table: landing
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name: agg
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type: Aggregate
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total_rows: 2
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data_compressed_bytes: 82
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data_uncompressed_bytes: 32
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sorting_key: ['user_id']
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query: SELECT user_id, max(date) AS max_date GROUP BY user_id
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```
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