spark-instrumented-optimizer/docs/sql-ref-syntax-aux-show-functions.md

---
layout: global
title: SHOW FUNCTIONS
displayTitle: SHOW FUNCTIONS
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  this work for additional information regarding copyright ownership.
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---

### Description

Returns the list of functions after applying an optional regex pattern.
Given number of functions supported by Spark is quite large, this statement
in conjunction with [describe function](sql-ref-syntax-aux-describe-function.html)
may be used to quickly find the function and understand its usage. The `LIKE` 
clause is optional and supported only for compatibility with other systems.

### Syntax

```sql
SHOW [ function_kind ] FUNCTIONS [ [ LIKE ] { function_name | regex_pattern } ]
```

### Parameters

* **function_kind**

    Specifies the name space of the function to be searched upon. The valid name spaces are :

    * **USER** - Looks up the function(s) among the user defined functions.
    * **SYSTEM** - Looks up the function(s) among the system defined functions.
    * **ALL** -  Looks up the function(s) among both user and system defined functions.

* **function_name**

    Specifies a name of an existing function in the system. The function name may be
    optionally qualified with a database name. If `function_name` is qualified with
    a database then the function is resolved from the user specified database, otherwise
    it is resolved from the current database.

    **Syntax:** `[ database_name. ] function_name`

* **regex_pattern**

    Specifies a regular expression pattern that is used to filter the results of the
    statement.

    * Except for `*` and `|` character, the pattern works like a regular expression.
    * `*` alone matches 0 or more characters and `|` is used to separate multiple different regular expressions,
       any of which can match.
    * The leading and trailing blanks are trimmed in the input pattern before processing. The pattern match is case-insensitive.

### Examples

```sql
-- List a system function `trim` by searching both user defined and system
-- defined functions.
SHOW FUNCTIONS trim;
+--------+
|function|
+--------+
|    trim|
+--------+

-- List a system function `concat` by searching system defined functions.
SHOW SYSTEM FUNCTIONS concat;
+--------+
|function|
+--------+
|  concat|
+--------+

-- List a qualified function `max` from database `salesdb`. 
SHOW SYSTEM FUNCTIONS salesdb.max;
+--------+
|function|
+--------+
|     max|
+--------+

-- List all functions starting with `t`
SHOW FUNCTIONS LIKE 't*';
+-----------------+
|         function|
+-----------------+
|              tan|
|             tanh|
|        timestamp|
|          tinyint|
|           to_csv|
|          to_date|
|          to_json|
|     to_timestamp|
|to_unix_timestamp|
| to_utc_timestamp|
|        transform|
|   transform_keys|
| transform_values|
|        translate|
|             trim|
|            trunc|
|           typeof|
+-----------------+

-- List all functions starting with `yea` or `windo`
SHOW FUNCTIONS LIKE 'yea*|windo*';
+--------+
|function|
+--------+
|  window|
|    year|
+--------+

-- Use normal regex pattern to list function names that has 4 characters
-- with `t` as the starting character.
SHOW FUNCTIONS LIKE 't[a-z][a-z][a-z]';
+--------+
|function|
+--------+
|    tanh|
|    trim|
+--------+
```

### Related Statements

* [DESCRIBE FUNCTION](sql-ref-syntax-aux-describe-function.html)