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392 lines
11 KiB
Markdown
392 lines
11 KiB
Markdown
---
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toc_priority: 48
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toc_title: Bit
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---
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# Bit Functions {#bit-functions}
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Bit functions work for any pair of types from `UInt8`, `UInt16`, `UInt32`, `UInt64`, `Int8`, `Int16`, `Int32`, `Int64`, `Float32`, or `Float64`. Some functions support `String` and `FixedString` types.
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The result type is an integer with bits equal to the maximum bits of its arguments. If at least one of the arguments is signed, the result is a signed number. If an argument is a floating-point number, it is cast to Int64.
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## bitAnd(a, b) {#bitanda-b}
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## bitOr(a, b) {#bitora-b}
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## bitXor(a, b) {#bitxora-b}
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## bitNot(a) {#bitnota}
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## bitShiftLeft(a, b) {#bitshiftlefta-b}
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Shifts the bit representation of a value to the left by a specified number of bit positions.
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A `FixedString` or a `String` are treated as a single multibyte value.
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Bits of a `FixedString` value are lost as they are shifted out. On the contrary, a `String` value is extended with additional bytes, so no bits are lost.
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**Syntax**
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``` sql
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bitShiftLeft(a, b)
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```
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**Arguments**
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- `a` — A value to shift. [Int/UInt](../../sql-reference/data-types/int-uint.md), [String](../../sql-reference/data-types/string.md), [FixedString](../../sql-reference/data-types/fixedstring.md).
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- `b` — The number of shifted positions. [UInt](../../sql-reference/data-types/int-uint.md), 64 bit types or less are allowed.
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**Returned value**
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- Shifted value.
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The type of a returned value is the same as the type of an input value.
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**Example**
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In the following queries [bin](encoding-functions.md#bin) and [hex](encoding-functions.md#hex) functions are used to show bits of shifted values.
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``` sql
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SELECT 99 AS a, bin(a), bitShiftLeft(a, 2) AS a_shifted, bin(a_shifted);
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SELECT 'abc' AS a, hex(a), bitShiftLeft(a, 4) AS a_shifted, hex(a_shifted);
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SELECT toFixedString('abc', 3) AS a, hex(a), bitShiftLeft(a, 4) AS a_shifted, hex(a_shifted);
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```
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Result:
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``` text
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┌──a─┬─bin(99)──┬─a_shifted─┬─bin(bitShiftLeft(99, 2))─┐
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│ 99 │ 01100011 │ 140 │ 10001100 │
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└────┴──────────┴───────────┴──────────────────────────┘
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┌─a───┬─hex('abc')─┬─a_shifted─┬─hex(bitShiftLeft('abc', 4))─┐
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│ abc │ 616263 │ &0 │ 06162630 │
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└─────┴────────────┴───────────┴─────────────────────────────┘
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┌─a───┬─hex(toFixedString('abc', 3))─┬─a_shifted─┬─hex(bitShiftLeft(toFixedString('abc', 3), 4))─┐
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│ abc │ 616263 │ &0 │ 162630 │
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└─────┴──────────────────────────────┴───────────┴───────────────────────────────────────────────┘
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```
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## bitShiftRight(a, b) {#bitshiftrighta-b}
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Shifts a value right by specified number of bit positions.
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A `FixedString` or a `String` are treated as a single multibyte value. Note that the length of a `String` value is reduced as bits are shifted out.
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**Syntax**
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``` sql
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bitShiftRight(a, b)
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```
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**Arguments**
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- `a` — A value to shift. [Int/UInt](../../sql-reference/data-types/int-uint.md), [String](../../sql-reference/data-types/string.md), [FixedString](../../sql-reference/data-types/fixedstring.md).
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- `b` — A count of positions. [Unsigned integer](../../sql-reference/data-types/int-uint.md), 64 bit types or less are allowed.
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**Returned value**
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- Shifted value.
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The type of a returned value is the same as the type of an input value.
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**Example**
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``` sql
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SELECT 101 AS a, bin(a), bitShiftRight(a, 2) AS a_shifted, bin(a_shifted);
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SELECT 'abc' AS a, hex(a), bitShiftRight(a, 12) AS a_shifted, hex(a_shifted);
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SELECT toFixedString('abc', 3) AS a, hex(a), bitShiftRight(a, 12) AS a_shifted, hex(a_shifted);
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```
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Result:
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``` text
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┌───a─┬─bin(101)─┬─a_shifted─┬─bin(bitShiftRight(101, 2))─┐
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│ 101 │ 01100101 │ 25 │ 00011001 │
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└─────┴──────────┴───────────┴────────────────────────────┘
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┌─a───┬─hex('abc')─┬─a_shifted─┬─hex(bitShiftRight('abc', 12))─┐
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│ abc │ 616263 │ │ 0616 │
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└─────┴────────────┴───────────┴───────────────────────────────┘
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┌─a───┬─hex(toFixedString('abc', 3))─┬─a_shifted─┬─hex(bitShiftRight(toFixedString('abc', 3), 12))─┐
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│ abc │ 616263 │ │ 000616 │
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└─────┴──────────────────────────────┴───────────┴─────────────────────────────────────────────────┘
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```
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## bitRotateLeft(a, b) {#bitrotatelefta-b}
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## bitRotateRight(a, b) {#bitrotaterighta-b}
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## bitTest {#bittest}
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Takes any integer and converts it into [binary form](https://en.wikipedia.org/wiki/Binary_number), returns the value of a bit at specified position. The countdown starts from 0 from the right to the left.
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**Syntax**
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``` sql
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SELECT bitTest(number, index)
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```
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**Arguments**
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- `number` – Integer number.
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- `index` – Position of bit.
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**Returned values**
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Returns a value of bit at specified position.
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Type: `UInt8`.
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**Example**
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For example, the number 43 in base-2 (binary) numeral system is 101011.
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Query:
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``` sql
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SELECT bitTest(43, 1);
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```
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Result:
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``` text
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┌─bitTest(43, 1)─┐
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│ 1 │
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└────────────────┘
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```
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Another example:
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Query:
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``` sql
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SELECT bitTest(43, 2);
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```
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Result:
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``` text
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┌─bitTest(43, 2)─┐
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│ 0 │
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└────────────────┘
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```
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## bitTestAll {#bittestall}
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Returns result of [logical conjuction](https://en.wikipedia.org/wiki/Logical_conjunction) (AND operator) of all bits at given positions. The countdown starts from 0 from the right to the left.
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The conjuction for bitwise operations:
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0 AND 0 = 0
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0 AND 1 = 0
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1 AND 0 = 0
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1 AND 1 = 1
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**Syntax**
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``` sql
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SELECT bitTestAll(number, index1, index2, index3, index4, ...)
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```
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**Arguments**
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- `number` – Integer number.
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- `index1`, `index2`, `index3`, `index4` – Positions of bit. For example, for set of positions (`index1`, `index2`, `index3`, `index4`) is true if and only if all of its positions are true (`index1` ⋀ `index2`, ⋀ `index3` ⋀ `index4`).
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**Returned values**
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Returns result of logical conjuction.
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Type: `UInt8`.
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**Example**
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For example, the number 43 in base-2 (binary) numeral system is 101011.
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Query:
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``` sql
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SELECT bitTestAll(43, 0, 1, 3, 5);
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```
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Result:
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``` text
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┌─bitTestAll(43, 0, 1, 3, 5)─┐
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│ 1 │
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└────────────────────────────┘
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```
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Another example:
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Query:
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``` sql
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SELECT bitTestAll(43, 0, 1, 3, 5, 2);
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```
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Result:
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``` text
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┌─bitTestAll(43, 0, 1, 3, 5, 2)─┐
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│ 0 │
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└───────────────────────────────┘
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```
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## bitTestAny {#bittestany}
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Returns result of [logical disjunction](https://en.wikipedia.org/wiki/Logical_disjunction) (OR operator) of all bits at given positions. The countdown starts from 0 from the right to the left.
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The disjunction for bitwise operations:
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0 OR 0 = 0
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0 OR 1 = 1
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1 OR 0 = 1
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1 OR 1 = 1
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**Syntax**
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``` sql
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SELECT bitTestAny(number, index1, index2, index3, index4, ...)
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```
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**Arguments**
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- `number` – Integer number.
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- `index1`, `index2`, `index3`, `index4` – Positions of bit.
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**Returned values**
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Returns result of logical disjuction.
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Type: `UInt8`.
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**Example**
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For example, the number 43 in base-2 (binary) numeral system is 101011.
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Query:
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``` sql
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SELECT bitTestAny(43, 0, 2);
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```
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Result:
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``` text
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┌─bitTestAny(43, 0, 2)─┐
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│ 1 │
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└──────────────────────┘
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```
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Another example:
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Query:
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``` sql
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SELECT bitTestAny(43, 4, 2);
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```
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Result:
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``` text
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┌─bitTestAny(43, 4, 2)─┐
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│ 0 │
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└──────────────────────┘
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```
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## bitCount {#bitcount}
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Calculates the number of bits set to one in the binary representation of a number.
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**Syntax**
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``` sql
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bitCount(x)
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```
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**Arguments**
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- `x` — [Integer](../../sql-reference/data-types/int-uint.md) or [floating-point](../../sql-reference/data-types/float.md) number. The function uses the value representation in memory. It allows supporting floating-point numbers.
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**Returned value**
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- Number of bits set to one in the input number.
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The function does not convert input value to a larger type ([sign extension](https://en.wikipedia.org/wiki/Sign_extension)). So, for example, `bitCount(toUInt8(-1)) = 8`.
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Type: `UInt8`.
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**Example**
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Take for example the number 333. Its binary representation: 0000000101001101.
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Query:
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``` sql
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SELECT bitCount(333);
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```
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Result:
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``` text
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┌─bitCount(333)─┐
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│ 5 │
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└───────────────┘
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```
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## bitHammingDistance {#bithammingdistance}
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Returns the [Hamming Distance](https://en.wikipedia.org/wiki/Hamming_distance) between the bit representations of two integer values. Can be used with [SimHash](../../sql-reference/functions/hash-functions.md#ngramsimhash) functions for detection of semi-duplicate strings. The smaller is the distance, the more likely those strings are the same.
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**Syntax**
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``` sql
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bitHammingDistance(int1, int2)
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```
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**Arguments**
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- `int1` — First integer value. [Int64](../../sql-reference/data-types/int-uint.md).
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- `int2` — Second integer value. [Int64](../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- The Hamming distance.
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Type: [UInt8](../../sql-reference/data-types/int-uint.md).
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**Examples**
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Query:
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``` sql
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SELECT bitHammingDistance(111, 121);
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```
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Result:
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``` text
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┌─bitHammingDistance(111, 121)─┐
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│ 3 │
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└──────────────────────────────┘
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```
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With [SimHash](../../sql-reference/functions/hash-functions.md#ngramsimhash):
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``` sql
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SELECT bitHammingDistance(ngramSimHash('cat ate rat'), ngramSimHash('rat ate cat'));
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```
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Result:
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``` text
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┌─bitHammingDistance(ngramSimHash('cat ate rat'), ngramSimHash('rat ate cat'))─┐
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│ 5 │
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└──────────────────────────────────────────────────────────────────────────────┘
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```
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