Appendix

Appendix

Data Types

type	examples
Integer	1, -1, 1234567
Double	2.3, -3.56, 232.4
Bool	TRUE, FALSE
Date	2020-06-10
Time	11:18:30
String	“HStreamDB”
Null	NULL

Keywords

keyword	description
`ABS`	absolute value
`ACOS`	arccosine
`ACOSH`	inverse hyperbolic cosine
`AND`	logical and operator
`ARRAY_CONTAIN`	given an array, checks if a search value is contained in the array
`ARRAY_DISTINCT`	returns an array of all the distinct values
`ARRAY_EXCEPT`	`ARRAY_DISTINCT` except for those also present in the second array
`ARRAY_INTERSECT`	returns an array of all the distinct elements from the intersection of both input arrays
`ARRAY_JOIN`	creates a flat string representation of all elements contained in the given array
`ARRAY_LENGTH`	return the length of the given array
`ARRAY_MAX`	returns the maximum value from the given array of primitive elements
`ARRAY_MIN`	returns the minimum value from the given array of primitive elements
`ARRAY_REMOVE`	removes all elements from the input array equal to the second argument
`ARRAY_SORT`	sort the given array
`ARRAY_UNION`	returns an array of all the distinct elements from the union of both input arrays
`AS`	stream or field name alias
`ASIN`	arcsine
`ASINH`	inverse hyperbolic sine
`ATAN`	arctangent
`ATANH`	inverse hyperbolic tangent
`AVG`	average function
`BETWEEN`	range operator, used with `AND`
`BY`	do something by certain conditions, used with `GROUP` or `ORDER`
`CEIL`	rounds a number UPWARDS to the nearest integer
`COS`	cosine
`COSH`	hyperbolic cosine
`COUNT`	count function
`CREATE`	create a stream / connector
`DATE`	prefix of date constant
`DAY`	interval unit
`DROP`	drop a stream
`EXP`	exponent
`FLOOR`	rounds a number DOWNWARDS to the nearest integer
`FORMAT`	specify the format of a stream
`FROM`	specify where to select data from
`GROUP`	group values by certain conditions, used with `BY`
`HAVING`	filter select values by a condition
`HOPPING`	hopping window
`IFNULL`	if the first argument is `NULL` returns the second, else the first
`INNER`	joining type, used with `JOIN`
`INSERT`	insert data into a stream, used with `INTO`
`INTERVAL`	prefix of interval constant
`INTO`	insert data into a stream, used with `INSERT`
`IS_ARRAY`	to determine if the given value is an array of values
`IS_BOOL`	to determine if the given value is a boolean
`IS_DATE`	to determine if the given value is a date value
`IS_FLOAT`	to determine if the given value is a float
`IS_INT`	to determine if the given value is an integer
`IS_MAP`	to determine if the given value is a map of values
`IS_NUM`	to determine if the given value is a number
`IS_STR`	to determine if the given value is a string
`IS_TIME`	to determine if the given value is a time value
`JOIN`	for joining two streams
`LEFT`	joining type, used with `JOIN`
`LEFT_TRIM`	trim spaces from the left end of a string
`LOG`	logarithm with base e
`LOG10`	logarithm with base 10
`LOG2`	logarithm with base 2
`MAX`	maximum function
`MIN`	minimum function
`MINUTE`	interval unit
`MONTH`	interval unit
`NOT`	logical not operator
`NULLIF`	returns `NULL` if the first argument is equal to the second, otherwise the first
`ON`	specify conditions, used with `JOIN`
`OR`	logical or operator
`ORDER`	sort values by certain conditions, used with `BY`
`OUTER`	joining type, used with `JOIN`
`REVERSE`	reverse a string
`RIGHT_TRIM`	trim spaces from the right end of a string
`ROUND`	rounds a number to the nearest integer
`SECOND`	interval unit
`SELECT`	query a stream
`SESSION`	session window
`SHOW`	show something to stdout
`SIGN`	return the sign of a numeric value as an INTEGER
`SIN`	sine
`SINH`	hyperbolic sine
`SQRT`	square root
`STREAM`	specify a stream, used with `CREATE`
`STRLEN`	get the length of a string
`SUM`	sum function
`TAN`	tangent
`TANH`	hyperbolic tangent
`TIME`	prefix of the time constant
`TO_LOWER`	convert a string to lowercase
`TO_STR`	convert a value to string
`TO_UPPER`	convert a string to uppercase
`TRIM`	trim spaces from both ends of a string
`TUMBLING`	tumbling window
`VALUES`	specify inserted data, used with `INSERT INTO`
`WEEK`	interval unit
`WHERE`	filter selected values by a condition
`WITH`	specify properties when creating a stream
`WITHIN`	specify time window when joining two streams
`YEAR`	interval unit

Operators

operator	description
`=`	equal to
`<>`	not equal to
`<`	less than
`>`	greater than
`<=`	less than or equal to
`>=`	greater than or equal to
`+`	addition
`-`	subtraction
`*`	multiplication
`.`	access field of a stream
`[]`	access item of a map or an array
`AND`	logical and operator
`OR`	logical or operator
`NOT`	logical not operator
`BETWEEN`	range operator

Scalar Functions

function	description
`ABS`	absolute value
`ACOS`	arccosine
`ACOSH`	inverse hyperbolic cosine
`ARRAY_CONTAIN`	given an array, checks if a search value is contained in the array
`ARRAY_DISTINCT`	returns an array of all the distinct values
`ARRAY_EXCEPT`	`ARRAY_DISTINCT` except for those also present in the second array
`ARRAY_INTERSECT`	returns an array of all the distinct elements from the intersection of both input arrays
`ARRAY_JOIN`	creates a flat string representation of all elements contained in the given array
`ARRAY_LENGTH`	return the length of the given array
`ARRAY_MAX`	returns the maximum value from the given array of primitive elements
`ARRAY_MIN`	returns the minimum value from the given array of primitive elements
`ARRAY_REMOVE`	removes all elements from the input array equal to the second argument
`ARRAY_SORT`	sort the given array
`ARRAY_UNION`	returns an array of all the distinct elements from the union of both input arrays
`ASIN`	arcsine
`ASINH`	inverse hyperbolic sine
`ATAN`	arctangent
`ATANH`	inverse hyperbolic tangent
`CEIL`	rounds a number UPWARDS to the nearest integer
`COS`	cosine
`COSH`	hyperbolic cosine
`EXP`	exponent
`FLOOR`	rounds a number DOWNWARDS to the nearest integer
`IFNULL`	if the first argument is `NULL` returns the second, else the first
`NULLIF`	returns `NULL` if the first argument is equal to the second, otherwise the first
`IS_ARRAY`	to determine if the given value is an array of values
`IS_BOOL`	to determine if the given value is a boolean
`IS_DATE`	to determine if the given value is a date value
`IS_FLOAT`	to determine if the given value is a float
`IS_INT`	to determine if the given value is an integer
`IS_MAP`	to determine if the given value is a map of values
`IS_NUM`	to determine if the given value is a number
`IS_STR`	to determine if the given value is a string
`IS_TIME`	to determine if the given value is a time value
`LEFT_TRIM`	trim spaces from the left end of a string
`LOG`	logarithm with base e
`LOG10`	logarithm with base 10
`LOG2`	logarithm with base 2
`REVERSE`	reverse a string
`RIGHT_TRIM`	trim spaces from the right end of a string
`ROUND`	rounds a number to the nearest integer
`SIGN`	return the sign of a numeric value as an INTEGER
`SIN`	sine
`SINH`	hyperbolic sine
`SQRT`	square root
`STRLEN`	get the length of a string
`TAN`	tangent
`TANH`	hyperbolic tangent
`TO_LOWER`	convert a string to lowercase
`TO_STR`	convert a value to string
`TO_UPPER`	convert a string to uppercase
`TRIM`	trim spaces from both ends of a string

Aggregate Functions

function	description
`AVG`	average
`COUNT`	count
`MAX`	maximum
`MIN`	minimum
`SUM`	sum