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Copy file name to clipboardExpand all lines: docs/faq/use-cases/key-value.md
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@@ -17,4 +17,4 @@ If you decide to go against recommendations and run some key-value-like queries
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- The key reason why point queries are expensive in ClickHouse is its sparse primary index of main [MergeTree table engine family](../..//engines/table-engines/mergetree-family/mergetree.md). This index can't point to each specific row of data, instead, it points to each N-th and the system has to scan from the neighboring N-th row to the desired one, reading excessive data along the way. In a key-value scenario, it might be useful to reduce the value of N with the `index_granularity` setting.
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- ClickHouse keeps each column in a separate set of files, so to assemble one complete row it needs to go through each of those files. Their count increases linearly with the number of columns, so in the key-value scenario, it might be worth avoiding using many columns and put all your payload in a single `String` column encoded in some serialization format like JSON, Protobuf, or whatever makes sense.
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- There's an alternative approach that uses [Join](../../engines/table-engines/special/join.md) table engine instead of normal `MergeTree` tables and [joinGet](../../sql-reference/functions/other-functions.md#joinget) function to retrieve the data. It can provide better query performance but might have some usability and reliability issues. Here's an [usage example](https://github.com/ClickHouse/ClickHouse/blob/master/tests/queries/0_stateless/00800_versatile_storage_join.sql#L49-L51).
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- There's an alternative approach that uses [Join](../../engines/table-engines/special/join.md) table engine instead of normal `MergeTree` tables and [joinGet](../../sql-reference/functions/other-functions.md#joinGet) function to retrieve the data. It can provide better query performance but might have some usability and reliability issues. Here's an [usage example](https://github.com/ClickHouse/ClickHouse/blob/master/tests/queries/0_stateless/00800_versatile_storage_join.sql#L49-L51).
Copy file name to clipboardExpand all lines: docs/guides/developer/merge-table-function.md
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```
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We use the [`variantType`](/docs/sql-reference/functions/other-functions#varianttype) function to check the type of `winner_seed` for each row and then [`variantElement`](/docs/sql-reference/functions/other-functions#variantelement) to extract the underlying value.
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We use the [`variantType`](/docs/sql-reference/functions/other-functions#variantType) function to check the type of `winner_seed` for each row and then [`variantElement`](/docs/sql-reference/functions/other-functions#variantElement) to extract the underlying value.
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When the type is `String`, we cast to a number and then do the comparison.
Copy file name to clipboardExpand all lines: docs/guides/generating-test-data.md
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@@ -147,7 +147,7 @@ Read the [Generating Random Data in ClickHouse](https://clickhouse.com/blog/gene
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## Generating random tables {#generating-random-tables}
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The [`generateRandomStructure`](/sql-reference/functions/other-functions#generaterandomstructure) function is particularly useful when combined with the [`generateRandom`](/sql-reference/table-functions/generate) table engine for testing, benchmarking, or creating mock data with arbitrary schemas.
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The [`generateRandomStructure`](/sql-reference/functions/other-functions#generateRandomStructure) function is particularly useful when combined with the [`generateRandom`](/sql-reference/table-functions/generate) table engine for testing, benchmarking, or creating mock data with arbitrary schemas.
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Let's start by just seeing what a random structure looks like using the `generateRandomStructure` function:
Copy file name to clipboardExpand all lines: docs/integrations/data-visualization/tableau/tableau-analysis-tips.md
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17.07.2004 14:01:56 | 11.07.2004 00:00:00
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14.07.2004 07:43:00 | 11.07.2004 00:00:00
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```
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- **`FORMAT_READABLE_QUANTITY([my_integer])`** *(added in v0.2.1)* — Returns a rounded number with a suffix (thousand, million, billion, etc.) as a string. It is useful for reading big numbers by human. Equivalent of [`formatReadableQuantity()`](/sql-reference/functions/other-functions#formatreadablequantity).
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- **`FORMAT_READABLE_TIMEDELTA([my_integer_timedelta_sec], [optional_max_unit])`** *(added in v0.2.1)* — Accepts the time delta in seconds. Returns a time delta with (year, month, day, hour, minute, second) as a string. `optional_max_unit` is maximum unit to show. Acceptable values: `seconds`, `minutes`, `hours`, `days`, `months`, `years`. Equivalent of [`formatReadableTimeDelta()`](/sql-reference/functions/other-functions/#formatreadabletimedelta).
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- **`GET_SETTING([my_setting_name])`** *(added in v0.2.1)* — Returns the current value of a custom setting. Equivalent of [`getSetting()`](/sql-reference/functions/other-functions#getsetting).
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- **`FORMAT_READABLE_QUANTITY([my_integer])`** *(added in v0.2.1)* — Returns a rounded number with a suffix (thousand, million, billion, etc.) as a string. It is useful for reading big numbers by human. Equivalent of [`formatReadableQuantity()`](/sql-reference/functions/other-functions#formatReadableQuantity).
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- **`FORMAT_READABLE_TIMEDELTA([my_integer_timedelta_sec], [optional_max_unit])`** *(added in v0.2.1)* — Accepts the time delta in seconds. Returns a time delta with (year, month, day, hour, minute, second) as a string. `optional_max_unit` is maximum unit to show. Acceptable values: `seconds`, `minutes`, `hours`, `days`, `months`, `years`. Equivalent of [`formatReadableTimeDelta()`](/sql-reference/functions/other-functions/#formatReadableTimeDelta).
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- **`GET_SETTING([my_setting_name])`** *(added in v0.2.1)* — Returns the current value of a custom setting. Equivalent of [`getSetting()`](/sql-reference/functions/other-functions#getSetting).
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- **`HEX([my_string])`** *(added in v0.2.1)* — Returns a string containing the argument's hexadecimal representation. Equivalent of [`hex()`](/sql-reference/functions/encoding-functions/#hex).
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- **`KURTOSIS([my_number])`** — Computes the sample kurtosis of a sequence. Equivalent of [`kurtSamp()`](/sql-reference/aggregate-functions/reference/kurtsamp).
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- **`KURTOSISP([my_number])`** — Computes the kurtosis of a sequence. The equivalent of [`kurtPop()`](/sql-reference/aggregate-functions/reference/kurtpop).
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- **`SHA256([my_string])`** *(added in v0.2.1)* — Calculates SHA-256 hash from a string and returns the resulting set of bytes as a string (FixedString). Convenient to use with the `HEX()` function, for example, `HEX(SHA256([my_string]))`. Equivalent of [`SHA256()`](/sql-reference/functions/hash-functions#SHA256).
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- **`SKEWNESS([my_number])`** — Computes the sample skewness of a sequence. Equivalent of [`skewSamp()`](/sql-reference/aggregate-functions/reference/skewsamp).
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- **`SKEWNESSP([my_number])`** — Computes the skewness of a sequence. Equivalent of [`skewPop()`](/sql-reference/aggregate-functions/reference/skewpop).
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- **`TO_TYPE_NAME([field])`** *(added in v0.2.1)* — Returns a string containing the ClickHouse type name of the passed argument. Equivalent of [`toTypeName()`](/sql-reference/functions/other-functions#totypename).
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- **`TO_TYPE_NAME([field])`** *(added in v0.2.1)* — Returns a string containing the ClickHouse type name of the passed argument. Equivalent of [`toTypeName()`](/sql-reference/functions/other-functions#toTypeName).
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- **`TRUNC([my_float])`** — It is the same as the `FLOOR([my_float])` function. Equivalent of [`trunc()`](/sql-reference/functions/rounding-functions#truncate).
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- **`UNHEX([my_string])`** *(added in v0.2.1)* — Performs the opposite operation of `HEX()`. Equivalent of [`unhex()`](/sql-reference/functions/encoding-functions#unhex).
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