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 SELECTed 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. |
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.
json_extract_path_text(col, ‘0', ‘forest')
