Hive - Built-in Functions

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This chapter explains the built-in functions available in Hive. The functions look quite similar to SQL functions, except for their usage.

Built-In Functions

Hive supports the following built-in functions:

Return Type Signature Description
BIGINT round(double a) It returns the rounded BIGINT value of the double.
BIGINT floor(double a) It returns the maximum BIGINT value that is equal or less than the double.
BIGINT ceil(double a) It returns the minimum BIGINT value that is equal or greater than the double.
double rand(), rand(int seed) It returns a random number that changes from row to row.
string concat(string A, string B,...) It returns the string resulting from concatenating B after A.
string substr(string A, int start) It returns the substring of A starting from start position till the end of string A.
string substr(string A, int start, int length) It returns the substring of A starting from start position with the given length.
string upper(string A) It returns the string resulting from converting all characters of A to upper case.
string ucase(string A) Same as above.
string lower(string A) It returns the string resulting from converting all characters of B to lower case.
string lcase(string A) Same as above.
string trim(string A) It returns the string resulting from trimming spaces from both ends of A.
string ltrim(string A) It returns the string resulting from trimming spaces from the beginning (left hand side) of A.
string rtrim(string A) rtrim(string A) It returns the string resulting from trimming spaces from the end (right hand side) of A.
string regexp_replace(string A, string B, string C) It returns the string resulting from replacing all substrings in B that match the Java regular expression syntax with C.
int size(Map<K.V>) It returns the number of elements in the map type.
int size(Array<T>) It returns the number of elements in the array type.
value of <type> cast(<expr> as <type>) It converts the results of the expression expr to <type> e.g. cast('1' as BIGINT) converts the string '1' to it integral representation. A NULL is returned if the conversion does not succeed.
string from_unixtime(int unixtime) convert the number of seconds from Unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the format of "1970-01-01 00:00:00"
string to_date(string timestamp) It returns the date part of a timestamp string: to_date("1970-01-01 00:00:00") = "1970-01-01"
int year(string date) It returns the year part of a date or a timestamp string: year("1970-01-01 00:00:00") = 1970, year("1970-01-01") = 1970
int month(string date) It returns the month part of a date or a timestamp string: month("1970-11-01 00:00:00") = 11, month("1970-11-01") = 11
int day(string date) It returns the day part of a date or a timestamp string: day("1970-11-01 00:00:00") = 1, day("1970-11-01") = 1
string get_json_object(string json_string, string path) It extracts json object from a json string based on json path specified, and returns json string of the extracted json object. It returns NULL if the input json string is invalid.

Example

The following queries demonstrate some built-in functions:

round() function

hive> SELECT round(2.6) from temp;

On successful execution of query, you get to see the following response:

3.0

floor() function

hive> SELECT floor(2.6) from temp;

On successful execution of the query, you get to see the following response:

2.0

ceil() function

hive> SELECT ceil(2.6) from temp;

On successful execution of the query, you get to see the following response:

3.0

Aggregate Functions

Hive supports the following built-in aggregate functions. The usage of these functions is as same as the SQL aggregate functions.

Return Type Signature Description
BIGINT count(*), count(expr), count(*) - Returns the total number of retrieved rows.
DOUBLE sum(col), sum(DISTINCT col) It returns the sum of the elements in the group or the sum of the distinct values of the column in the group.
DOUBLE avg(col), avg(DISTINCT col) It returns the average of the elements in the group or the average of the distinct values of the column in the group.
DOUBLE min(col) It returns the minimum value of the column in the group.
DOUBLE max(col) It returns the maximum value of the column in the group.
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