GROUPING_ID

Name

GROUPING_ID

Description

Is a function that computes the level of grouping. GROUPING_ID can be used only in the SELECT <select> list, HAVING, or ORDER BY clauses when GROUP BY is specified.

Syntax

GROUPING_ID ( <column_expression>[ ,...n ] )

Arguments

<column_expression>

Is a column_expression in a GROUP BY clause.

Return Type

BIGINT

Remarks

The GROUPING_ID’s <column_expression> must exactly match the expression in the GROUP BY list. For example, if you are grouping by user_id, use GROUPING_ID (user_id); or if you are grouping by name, use GROUPING_ID (name).

Comparing GROUPING_ID() to GROUPING()

GROUPING_ID(<column_expression> [ ,...n ]) inputs the equivalent of the GROUPING(<column_expression>) return for each column in its column list in each output row as a string of ones and zeros. GROUPING_ID interprets that string as a base-2 number and returns the equivalent integer. For example consider the following statement: SELECT a, b, c, SUM(d), GROUPING_ID(a,b,c) FROM T GROUP BY <group by list>. The following table shows the GROUPING_ID() input and output values.

Technical Definition of GROUPING_ID()

Each GROUPING_ID argument must be an element of the GROUP BY list. GROUPING_ID() returns an integer bitmap whose lowest N bits may be lit. A lit bit indicates the corresponding argument is not a grouping column for the given output row. The lowest-order bit corresponds to argument N, and the (N-1)ᵗʰ lowest-order bit corresponds to argument 1.

GROUPING_ID() Equivalents

For a single grouping query, GROUPING (<column_expression>) is equivalent to GROUPING_ID(<column_expression>), and both return 0. For example, the following statements are equivalent:

Statement A:

SELECT GROUPING_ID(A,B)  
FROM T   
GROUP BY CUBE(A,B)

Statement B:

SELECT 3 FROM T GROUP BY ()  
UNION ALL  
SELECT 1 FROM T GROUP BY A  
UNION ALL  
SELECT 2 FROM T GROUP BY B  
UNION ALL  
SELECT 0 FROM T GROUP BY A,B

Example

Before starting our example, We first prepare the following data.

CREATE TABLE employee (
  uid        INT,
  name       VARCHAR(32),
  level      VARCHAR(32),
  title      VARCHAR(32),
  department VARCHAR(32),
  hiredate   DATE
)
UNIQUE KEY(uid)
DISTRIBUTED BY HASH(uid) BUCKETS 1
PROPERTIES (
  "replication_num" = "1"
);
INSERT INTO employee VALUES
  (1, 'Abby', 'Senior', 'President', 'Board of Directors', '1999-11-13'),
  (2, 'Bob', 'Senior', 'Vice-President', 'Board of Directors', '1999-11-13'),
  (3, 'Candy', 'Senior', 'System Engineer', 'Technology', '2005-3-7'),
  (4, 'Devere', 'Senior', 'Hardware Engineer', 'Technology', '2006-7-9'),
  (5, 'Emilie', 'Senior', 'System Analyst', 'Technology', '2003-8-28'),
  (6, 'Fredrick', 'Senior', 'Sales Manager', 'Sales', '2004-9-7'),
  (7, 'Gitel', 'Assistant', 'Business Executive', 'Sales', '2003-3-19'),
  (8, 'Haden', 'Trainee', 'Sales Assistant', 'Sales', '2007-6-30'),
  (9, 'Irene', 'Assistant', 'Business Executive', 'Sales', '2005-10-20'),
  (10, 'Jankin', 'Senior', 'Marketing Supervisor', 'Marketing', '2001-4-13'),
  (11, 'Louis', 'Trainee', 'Marketing Assistant', 'Marketing', '2007-8-2'),
  (12, 'Martin', 'Trainee', 'Marketing Assistant', 'Marketing', '2007-7-1'),
  (13, 'Nasir', 'Assistant', 'Marketing Executive', 'Marketing', '2004-9-3');

Here is the result.

+------+----------+-----------+----------------------+--------------------+------------+
| uid  | name     | level     | title                | department         | hiredate   |
+------+----------+-----------+----------------------+--------------------+------------+
|    1 | Abby     | Senior    | President            | Board of Directors | 1999-11-13 |
|    2 | Bob      | Senior    | Vice-President       | Board of Directors | 1999-11-13 |
|    3 | Candy    | Senior    | System Engineer      | Technology         | 2005-03-07 |
|    4 | Devere   | Senior    | Hardware Engineer    | Technology         | 2006-07-09 |
|    5 | Emilie   | Senior    | System Analyst       | Technology         | 2003-08-28 |
|    6 | Fredrick | Senior    | Sales Manager        | Sales              | 2004-09-07 |
|    7 | Gitel    | Assistant | Business Executive   | Sales              | 2003-03-19 |
|    8 | Haden    | Trainee   | Sales Assistant      | Sales              | 2007-06-30 |
|    9 | Irene    | Assistant | Business Executive   | Sales              | 2005-10-20 |
|   10 | Jankin   | Senior    | Marketing Supervisor | Marketing          | 2001-04-13 |
|   11 | Louis    | Trainee   | Marketing Assistant  | Marketing          | 2007-08-02 |
|   12 | Martin   | Trainee   | Marketing Assistant  | Marketing          | 2007-07-01 |
|   13 | Nasir    | Assistant | Marketing Executive  | Marketing          | 2004-09-03 |
+------+----------+-----------+----------------------+--------------------+------------+
13 rows in set (0.01 sec)

A. Using GROUPING_ID to identify grouping levels

The following example returns the count of employees by department and level. GROUPING_ID() is used to create a value for each row in the Job Title column that identifies its level of aggregation.

SELECT
  department,
  CASE 
    WHEN GROUPING_ID(department, level) = 0 THEN level
    WHEN GROUPING_ID(department, level) = 1 THEN CONCAT('Total: ', department)
    WHEN GROUPING_ID(department, level) = 3 THEN 'Total: Company'
    ELSE 'Unknown'
  END AS 'Job Title',
  COUNT(uid) AS 'Employee Count'
FROM employee 
GROUP BY ROLLUP(department, level)
ORDER BY GROUPING_ID(department, level) ASC;

Here is the result.

+--------------------+---------------------------+----------------+
| department         | Job Title                 | Employee Count |
+--------------------+---------------------------+----------------+
| Board of Directors | Senior                    |              2 |
| Technology         | Senior                    |              3 |
| Sales              | Senior                    |              1 |
| Sales              | Assistant                 |              2 |
| Sales              | Trainee                   |              1 |
| Marketing          | Senior                    |              1 |
| Marketing          | Trainee                   |              2 |
| Marketing          | Assistant                 |              1 |
| Board of Directors | Total: Board of Directors |              2 |
| Technology         | Total: Technology         |              3 |
| Sales              | Total: Sales              |              4 |
| Marketing          | Total: Marketing          |              4 |
| NULL               | Total: Company            |             13 |
+--------------------+---------------------------+----------------+
13 rows in set (0.01 sec)

B. Using GROUPING_ID to filter a result set

In the following code, to return only the rows that have the count of senior in department.

SELECT
  department,
  CASE 
    WHEN GROUPING_ID(department, level) = 0 THEN level
    WHEN GROUPING_ID(department, level) = 1 THEN CONCAT('Total: ', department)
    WHEN GROUPING_ID(department, level) = 3 THEN 'Total: Company'
    ELSE 'Unknown'
  END AS 'Job Title',
  COUNT(uid)
FROM employee 
GROUP BY ROLLUP(department, level)
HAVING `Job Title` IN ('Senior');

Here is the result.

+--------------------+-----------+--------------+
| department         | Job Title | count(`uid`) |
+--------------------+-----------+--------------+
| Board of Directors | Senior    |            2 |
| Technology         | Senior    |            3 |
| Sales              | Senior    |            1 |
| Marketing          | Senior    |            1 |
+--------------------+-----------+--------------+
5 rows in set (0.01 sec)

Keywords

GROUPING_ID

Best Practice

For more information, see also:

• GROUPING