DDSQL Functions

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Aggregation functions

Aggregate functions compute a single result from a set of input values, usually used in conjunction with a GROUP BY statement.

avg

Name	Argument Types	Return type	Description
avg(expr e)	numeric	numeric	Computes the average (arithmetic mean) of all the non-null input values.

max

Name	Argument Types	Return type	Description
max(expr e)	variable	variable	Computes the maximum of the non-null input values. Types of input values must be comparable.

min

Name	Argument Types	Return type	Description
min(expr e)	variable	variable	Computes the minimum of the non-null input values. Types of input values must be comparable.

sum

Name	Argument Types	Return type	Description
sum(expr e)	numeric	numeric	Computes the sum of the non-null input values.

count

Name	Argument Types	Return type	Description
count(expr e)	numeric	integer	Computes the number of input rows in which the input value is not null.
count(distinct expr e1, e2 …)		integer	Computes the number of input values in which the input value is not null.
count(*)		integer	Computes the number of input rows.

string_agg

Name	Argument Types	Return type	Description
string_agg(expr e, delimiter e)	string, string	string	Concatenates the input values, seperated by a delimiter.

array_agg

Name	Argument Types	Return type	Description
string_agg(expr e)	variable	array	Concatenates the input values into an array.

Scalar functions

These functions return one value per row.

String functions and operators

Name	Return type	Description
upper(text s)	text	Converts s to uppercase.
lower(text s)	text	Converts s to lowercase.
length(text s)	integer	Counts the number of characters in s.
concat(expr x, y, …)	text	Concatenates the provided expressions.
substr(expr s, numeric start, numeric numChars)	text	Returns a substring of s from start to a max of numChars, if provided. start is a 1-based index, so `substr('hello', 2)` returns `'ello'`. If the start is less than 1, it is treated as if it were 1. The result is computed by taking the range of characters `[start, start+numChars]`, where if any value is less than 1, it is treated as 1. This means `substr('hello', -2, 4)` returns `'h'`.
replace(text s, text from, text to)	text	Replaces all occurrences in s of substring from with substring to.
regexp_replace(text s, text pattern, text replacement)	text	Replace substrings in s that match the POSIX regular expression pattern with the replacement. Supports Go’s regular expression syntax.
reverse(expr text)	string	Reverses the string (brown → nworb).
md5(expr text)	string	Calculates the MD5 hash of a string and returns the result in hexadecimal.
char_length(str text)	integer	Returns number of characters in str.
left(str text, n int)	text	Returns first n characters in str. When n is negative, return all but last \|n\| characters.
right(str text, n int)	text	Returns last n characters in str. When n is negative, return all but first \|n\| characters.
ltrim(str text [, characters text])	text	Removes the longest string containing only characters from characters (a space by default) from the start of str.
rtrim(str text [, characters text])	text	Removes the longest string containing only characters from characters (a space by default) from the end of str
trim([leading \| trailing \| both] [characters] from str)	text	Removes the longest string containing only the characters (a space by default) from the start/end/both ends of str.
sort_order_ip(ip text)	text	Returns a string representing a sort order over IPv4 and IPv6 range.

Mathematical functions and operators

Name	Return type	Description
abs(numeric n)	integer	Returns the absolute value of n.
round(numeric n, [s])	numeric	Round n to s decimal places.
mod(numeric x, numeric y)	integer	Returns the remainder of `x / y`.
floor(numeric n)	numeric	Returns the nearest integer that is less than or equal to n.
ceil(numeric n)	numeric	Returns the nearest integer that is greater than or equal to n.
power(numeric n, numeric s)	numeric	Raises n to the s power.
ln(numeric n)	numeric	Calculates the natural logarithm of n.
log(numeric n)	numeric	Calculates the logarithm to base 10 of n.
log2(numeric n)	numeric	Calculates the logarithm to base 2 of n.
exp(numeric n)	numeric	Returns the mathematical constant e, raised to the power of n.
sqrt(numeric n)	numeric	Calculates the square root of n.

Array functions and operators

Name	Return type	Description
array_length(array a)	integer	Returns the length of the array a for each row.
array_contains(array a, expr e)	boolean	Returns true if the value the expr e evaluates to is in the array a for each row.
array_cat(array a, array b)	array	Returns a new array containing the combined elements from array a and array b.
array_append(array a, expr e)	array	Returns a new array that includes all the original elements of the input array followed by the appended element.
string_to_array(text s, delimiter, [,nullString])	array	Returns an array of substrings obtained by splitting the input string s, using the specified delimiter. The third argument, nullString, is optional and specifies substrings that are replaced with `NULL`.
array_to_string(array a, delimiter, [,nullString])	string	Concatenates array elements using supplied delimiter and optional null string.
unnest(array a)	variable	Returns each element in the array as a separate row. The return type is the element type of the array. `unnest` can only be used in the `SELECT` clause of a query. If other columns are `SELECT`ed with unnest, the value at each row in the table is repeated at each output row with each unnested element. If multiple columns are being unnested, all the unnested columns are zipped up together, with `NULL` filling in the output values for shorter arrays.

Date/time functions and operators

Name	Return type	Description
date_trunc(string precision, timestamp t)	timestamp	Truncates the timestamp to the chosen precision (“second”, “minute”, “hour”, “day”, “week”, “month”, or “year”).
date_diff(string precision, timestamp t, timestamp t)	integer	Returns the difference between two dates, in the precision specified.
to_timestamp(numeric n)	timestamp	Transforms n into a timestamp, considering n as the time in seconds.

Conditional expressions

Name	Return type	Description
coalesce(expr x, y, …)	variable	Returns the first non-null expression.
nullif(expr x, expr y)	variable	Returns `NULL` if both arguments are equal. Otherwise, returns x.

JSON functions and operators

Name	Return type	Description
json_extract_path_text(text json, text path…)	text	Extracts the JSON sub-object in JSON as text, defined by the path. Its behavior is equivalent to the postgres function with the same name. For example, `json_extract_path_text(col, ‘forest')` returns the value of the key `forest` for each JSON object in `col`. See the example below for a JSON array syntax.
json_extract_path(text json, text path…)	json	Same functionality as `json_extract_path_text`, but returns a column of JSON type instead of text type.
json_build_object(key1 text, value1 json/text/int/float, key2 text, value2 json/text/int/float, … )	json	Builds a JSON object based on the parameters passed in. The parameters to the function are the keys/values of the JSON object being built, alternating between key and value mapped to each key.
row_to_json(table)	json	Returns a JSON representation of each row in a table as a JSON value. The JSON keys are the column names, and the values are the values under each row at each column. Note: row_to_json takes in a table name, NOT a column, for example, `SELECT row_to_json(<table>) FROM <table>`.

JSON array

Return the value of the key forest in the 0th element in a JSON array for each JSON object or row in col.

[{
"forest": "trees"
}]

json_extract_path_text(col, ‘0', ‘forest')