308 lines
7.0 KiB
Markdown
308 lines
7.0 KiB
Markdown
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Use InfluxQL mathematical operators to perform mathematical operations in queries.
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Mathematical operators follow the [standard order of operations](https://golang.org/ref/spec#Operator_precedence).
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Parentheses take precedence to division and multiplication, which takes precedence to addition and subtraction.
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For example `5 / 2 + 3 * 2 = (5 / 2) + (3 * 2)` and `5 + 2 * 3 - 2 = 5 + (2 * 3) - 2`.
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- [Addition](#addition)
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- [Subtraction](#subtraction)
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- [Multiplication](#multiplication)
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- [Division](#division)
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- [Modulo](#modulo)
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- [Bitwise AND](#bitwise-and)
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- [Bitwise OR](#bitwise-or)
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- [Bitwise Exclusive-OR](#bitwise-exclusive-or)
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- [Unsupported Operators](#unsupported-operators)
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- [Common Issues with Mathematical Operators](#common-issues-with-mathematical-operators)
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## Addition
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Perform addition with a constant.
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```sql
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SELECT "A" + 5 FROM "add"
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```
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```sql
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SELECT * FROM "add" WHERE "A" + 5 > 10
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```
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Perform addition on two fields.
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```sql
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SELECT "A" + "B" FROM "add"
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```
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```sql
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SELECT * FROM "add" WHERE "A" + "B" >= 10
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```
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## Subtraction
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Perform subtraction with a constant.
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```sql
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SELECT 1 - "A" FROM "sub"
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```
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```sql
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SELECT * FROM "sub" WHERE 1 - "A" <= 3
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```
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Perform subtraction with two fields.
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```sql
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SELECT "A" - "B" FROM "sub"
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```
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```sql
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SELECT * FROM "sub" WHERE "A" - "B" <= 1
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```
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## Multiplication
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Perform multiplication with a constant.
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```sql
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SELECT 10 * "A" FROM "mult"
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```
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```sql
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SELECT * FROM "mult" WHERE "A" * 10 >= 20
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```
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Perform multiplication with two fields.
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```sql
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SELECT "A" * "B" * "C" FROM "mult"
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```
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```sql
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SELECT * FROM "mult" WHERE "A" * "B" <= 80
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```
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Multiplication distributes across other operators.
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```sql
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SELECT 10 * ("A" + "B" + "C") FROM "mult"
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```
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```sql
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SELECT 10 * ("A" - "B" - "C") FROM "mult"
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```
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```sql
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SELECT 10 * ("A" + "B" - "C") FROM "mult"
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```
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## Division
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Perform division with a constant.
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```sql
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SELECT 10 / "A" FROM "div"
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```
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```sql
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SELECT * FROM "div" WHERE "A" / 10 <= 2
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```
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Perform division with two fields.
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```sql
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SELECT "A" / "B" FROM "div"
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```
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```sql
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SELECT * FROM "div" WHERE "A" / "B" >= 10
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```
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Division distributes across other operators.
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```sql
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SELECT 10 / ("A" + "B" + "C") FROM "mult"
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```
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## Modulo
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Perform modulo arithmetic with a constant.
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```sql
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SELECT "B" % 2 FROM "modulo"
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```
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```sql
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SELECT "B" FROM "modulo" WHERE "B" % 2 = 0
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```
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Perform modulo arithmetic on two fields.
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```sql
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SELECT "A" % "B" FROM "modulo"
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```
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```sql
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SELECT "A" FROM "modulo" WHERE "A" % "B" = 0
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```
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## Bitwise AND
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You can use this operator with any integers or Booleans, whether they are fields or constants.
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It does not work with float or string datatypes, and you cannot mix integers and Booleans.
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```sql
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SELECT "A" & 255 FROM "bitfields"
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```
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```sql
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SELECT "A" & "B" FROM "bitfields"
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```
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```sql
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SELECT * FROM "data" WHERE "bitfield" & 15 > 0
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```
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```sql
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SELECT "A" & "B" FROM "booleans"
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```
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```sql
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SELECT ("A" ^ true) & "B" FROM "booleans"
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```
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## Bitwise OR
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You can use this operator with any integers or Booleans, whether they are fields or constants.
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It does not work with float or string datatypes, and you cannot mix integers and Booleans.
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```sql
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SELECT "A" | 5 FROM "bitfields"
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```
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```sql
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SELECT "A" | "B" FROM "bitfields"
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```
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```sql
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SELECT * FROM "data" WHERE "bitfield" | 12 = 12
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```
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## Bitwise Exclusive-OR
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You can use this operator with any integers or Booleans, whether they are fields or constants.
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It does not work with float or string datatypes, and you cannot mix integers and Booleans.
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```sql
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SELECT "A" ^ 255 FROM "bitfields"
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```
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```sql
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SELECT "A" ^ "B" FROM "bitfields"
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```
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```sql
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SELECT * FROM "data" WHERE "bitfield" ^ 6 > 0
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```
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## Unsupported Operators
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### Inequalities
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Using any of `=`,`!=`,`<`,`>`,`<=`,`>=`,`<>` in the `SELECT` statement yields empty results for all types.
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Comparison operators can only be used in the `WHERE` clause.
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### Logical Operators
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Using any of `!|`,`NAND`,`XOR`,`NOR` yield a parser error.
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Additionally using `AND`, `OR` in the `SELECT` clause of a query will not behave
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as mathematical operators and simply yield empty results, as they are tokens in InfluxQL.
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However, you can apply the bitwise operators `&`, `|` and `^` to boolean data.
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### Bitwise Not
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There is no bitwise-not operator, because the results you expect depend on the width of your bitfield.
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InfluxQL does not know how wide your bitfield is, so cannot implement a suitable bitwise-not operator.
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For example, if your bitfield is 8 bits wide, then to you the integer 1 represents the bits `0000 0001`.
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The bitwise-not of this should return the bits `1111 1110`, i.e. the integer 254.
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However, if your bitfield is 16 bits wide, then the integer 1 represents the bits `0000 0000 0000 0001`.
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The bitwise-not of this should return the bits `1111 1111 1111 1110`, i.e. the integer 65534.
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#### Solution
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You can implement a bitwise-not operation by using the `^` (bitwise xor) operator
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together with the number representing all-ones for your word-width:
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For 8-bit data:
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```sql
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SELECT "A" ^ 255 FROM "data"
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```
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For 16-bit data:
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```sql
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SELECT "A" ^ 65535 FROM "data"
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```
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For 32-bit data:
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```sql
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SELECT "A" ^ 4294967295 FROM "data"
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```
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In each case the constant you need can be calculated as `(2 ** width) - 1`.
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## Common Issues with Mathematical Operators
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- [Mathematical operators with wildcards and regular expressions](#mathematical-operators-with-wildcards-and-regular-expressions)
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- [Mathematical operators with functions](#mathematical-operators-with-functions)
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### Mathematical operators with wildcards and regular expressions
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InfluxDB does not support combining mathematical operations with a wildcard (`*`) or [regular expression](/influxdb/version/query-data/influxql/explore-data/regular-expressions/) in the `SELECT` clause.
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The following queries are invalid and the system returns an error:
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Perform a mathematical operation on a wildcard.
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```sql
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SELECT * + 2 FROM "nope"
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-- ERR: unsupported expression with wildcard: * + 2
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```
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Perform a mathematical operation on a wildcard within a function.
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```sql
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SELECT COUNT(*) / 2 FROM "nope"
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-- ERR: unsupported expression with wildcard: count(*) / 2
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```
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Perform a mathematical operation on a regular expression.
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```sql
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SELECT /A/ + 2 FROM "nope"
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-- ERR: error parsing query: found +, expected FROM at line 1, char 12
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```
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Perform a mathematical operation on a regular expression within a function.
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```sql
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SELECT COUNT(/A/) + 2 FROM "nope"
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-- ERR: unsupported expression with regex field: count(/A/) + 2
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```
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### Mathematical operators with functions
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The use of mathematical operators inside of function calls is currently unsupported.
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Note that InfluxDB only allows functions in the `SELECT` clause.
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For example, the following will work:
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```sql
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SELECT 10 * mean("value") FROM "cpu"
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```
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However, the following query will return a parse error:
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```sql
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SELECT mean(10 * "value") FROM "cpu"
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-- Error: expected field argument in mean()
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```
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{{% note %}}
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InfluxQL supports [subqueries](/influxdb/version/query-data/influxql/explore-data/subqueries/) which offer similar functionality to using mathematical operators inside a function call.
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{{% /note %}}
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