# Postgres functions

Get started with commonly-used Postgres functions with Neon's function guides. For other functions that Postgres supports, visit the official Postgres [Functions and Operators](https://www.postgresql.org/docs/current/functions.html) documentation.

## Aggregate functions

- [array\_agg()](/guides/postgres-functions-array-agg): Aggregate elements into an array
- [avg()](/guides/postgres-functions-avg): Calculate the average of a set of values
- [count()](/guides/postgres-functions-count): Count rows or non-null values in a result set
- [max()](/guides/postgres-functions-max): Find the maximum value in a set of values
- [sum()](/guides/postgres-functions-sum): Calculate the sum of a set of values

## Array functions

- [array\_length()](/guides/postgres-functions-array-length): Determine the length of an array

## Date / Time functions

- [age()](/guides/postgres-functions-age): Calculate the difference between timestamps or between a timestamp and the current date/time
- [current\_timestamp](/guides/postgres-functions-current-timestamp): Get the current date and time
- [date\_trunc()](/guides/postgres-functions-date-trunc): Truncate date/time values to a specified precision
- [extract()](/guides/postgres-functions-extract): Extract date and time components from timestamps and intervals
- [now()](/guides/postgres-functions-now): Get the current date and time

## JSON functions

- [array\_to\_json()](/guides/postgres-functions-array-to-json): Convert an SQL array to a JSON array
- [json()](/guides/postgres-functions-json): Transform JSON data into relational views
- [json\_agg()](/guides/postgres-functions-json-agg): Aggregate values into a JSON array
- [json\_array\_elements()](/guides/postgres-functions-json-array-elements): Expand a JSON array into a set of rows
- [jsonb\_array\_elements()](/guides/postgres-functions-jsonb-array-elements): Expand a JSONB array into a set of rows
- [json\_build\_object()](/guides/postgres-functions-json-build-object): Build a JSON object out of a variadic argument list
- [json\_each()](/guides/postgres-functions-json-each): Expand JSON into a record per key-value pair
- [json\_exists()](/guides/postgres-functions-json-exists): Check for Values in JSON Data Using SQL/JSON Path Expressions
- [json\_extract\_path()](/guides/postgres-functions-json-extract-path): Extract a JSON sub-object at the specified path
- [json\_extract\_path\_text()](/guides/postgres-functions-json-extract-path-text): Extract a JSON sub-object at the specified path as text
- [json\_object()](/guides/postgres-functions-json-object): Create a JSON object from key-value pairs
- [json\_populate\_record()](/guides/postgres-functions-json-populate-record): Cast a JSON object to a record
- [json\_query()](/guides/postgres-functions-json-query): Extract and Transform JSON Values with SQL/JSON Path Expressions
- [json\_scalar()](/guides/postgres-functions-json-scalar): Convert Text and Binary Data to JSON Values
- [json\_serialize()](/guides/postgres-functions-json-serialize): Convert JSON Values to Text or Binary Format
- [json\_table()](/guides/postgres-functions-json-table): Transform JSON data into relational views
- [json\_to\_record()](/guides/postgres-functions-json-to-record): Convert a JSON object to a record
- [json\_value()](/guides/postgres-functions-json-value): Extract and Convert JSON Scalar Values
- [jsonb\_each()](/guides/postgres-functions-jsonb-each): Expand JSONB into a record per key-value pair
- [jsonb\_extract\_path()](/guides/postgres-functions-jsonb-extract-path): Extract a JSONB sub-object at the specified path
- [jsonb\_extract\_path\_text()](/guides/postgres-functions-jsonb-extract-path-text): Extract a JSONB sub-object at the specified path as text
- [jsonb\_object()](/guides/postgres-functions-jsonb-object): Create a JSONB object from key-value pairs
- [jsonb\_populate\_record()](/guides/postgres-functions-jsonb-populate-record): Cast a JSONB object to a record
- [jsonb\_to\_record()](/guides/postgres-functions-jsonb-to-record): Convert a JSONB object to a record

## Mathematical functions

- [abs()](/guides/postgres-functions-math-abs): Calculate the absolute value of a number
- [random()](/guides/postgres-functions-math-random): Generate a random number between 0 and 1
- [round()](/guides/postgres-functions-math-round): Round numbers to a specified precision

## String functions

- [concat()](/guides/postgres-functions-concat): Concatenate strings
- [lower()](/guides/postgres-functions-lower): Convert a string to lowercase
- [substring()](/guides/postgres-functions-substring): Extract a substring from a string
- [regexp\_match()](/guides/postgres-functions-regexp-match): Extract substrings matching a regular expression pattern
- [regexp\_replace()](/guides/postgres-functions-regexp-replace): Replace substrings matching a regular expression pattern
- [trim()](/guides/postgres-functions-trim): Remove leading and trailing characters from a string

## Window functions

- [dense\_rank()](/guides/postgres-functions-dense-rank): Return the rank of the current row without gaps
- [lag()](/guides/postgres-functions-window-lag): Access values from previous rows in a result set
- [lead()](/guides/postgres-functions-window-lead): Access values from subsequent rows in a result set
- [rank()](/guides/postgres-functions-window-rank): Assign ranks to rows within a result set

## Related pages

- [Postgres data types](./postgres-data-types-introduction.md)
- [Postgres indexes](./postgres-postgresql-index-types.md)
- [Optimize Postgres query performance](./postgres-postgresql-query-performance.md)
- [Postgres query reference](./postgres-postgresql-query-reference.md)
- [Row-Level Security with Neon](./postgres-guides-row-level-security.md)
- [Postgres version support](./postgres-postgresql-postgres-version-support.md)
- [Upgrading your Postgres version](./postgres-postgresql-postgres-upgrade.md)
- [Postgres compatibility](./postgres-reference-compatibility.md)
- [Postgres array_agg() function](./postgres-functions-array-agg.md)
- [Postgres array_length() function](./postgres-functions-array-length.md)
- [Postgres age() function](./postgres-functions-age.md)
- [Postgres arraytojson() function](./postgres-functions-array-to-json.md)
- [Postgres dense_rank() function](./postgres-functions-dense-rank.md)
- [Postgres concat() function](./postgres-functions-concat.md)
- [Postgres abs() function](./postgres-functions-math-abs.md)

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