SQLite - GROUP BY

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The SQLite GROUP BY clause is used in collaboration with the SELECT statement to arrange identical data into groups.

The GROUP BY clause follows the WHERE clause in a SELECT statement and precedes the ORDER BY clause.

Syntax:

The basic syntax of GROUP BY clause is given below. The GROUP BY clause must follow the conditions in the WHERE clause and must precede the ORDER BY clause if one is used.

SELECT column-list
FROM table_name
WHERE [ conditions ]
GROUP BY column1, column2....columnN
ORDER BY column1, column2....columnN

You can use more than one column in the GROUP BY clause. Make sure whatever column you are using to group, that column should be available in column-list.

Example:

Consider COMPANY table is having the following records:

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

If you want to know the total amount of salary on each customer, then GROUP BY query would be as follows:

sqlite> SELECT NAME, SUM(SALARY) FROM COMPANY GROUP BY NAME;

This would produce following result:

NAME        SUM(SALARY)
----------  -----------
Allen       15000.0
David       85000.0
James       10000.0
Kim         45000.0
Mark        65000.0
Paul        20000.0
Teddy       20000.0

Now, let us create three more records in COMPANY table using the following INSERT statements:

INSERT INTO COMPANY VALUES (8, 'Paul', 24, 'Houston', 20000.00 );
INSERT INTO COMPANY VALUES (9, 'James', 44, 'Norway', 5000.00 );
INSERT INTO COMPANY VALUES (10, 'James', 45, 'Texas', 5000.00 );

Now, our table has the following records with duplicate names:

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0
8           Paul        24          Houston     20000.0
9           James       44          Norway      5000.0
10          James       45          Texas       5000.0

Again, let us use the same statement to group-by all the records using NAME column as follows:

sqlite> SELECT NAME, SUM(SALARY) FROM COMPANY GROUP BY NAME ORDER BY NAME;

This would produce the following result:

NAME        SUM(SALARY)
----------  -----------
Allen       15000
David       85000
James       20000
Kim         45000
Mark        65000
Paul        40000
Teddy       20000

Let us use ORDER BY clause along with GROUP BY clause as follows:

sqlite>  SELECT NAME, SUM(SALARY) 
         FROM COMPANY GROUP BY NAME ORDER BY NAME DESC;

This would produce the following result:

NAME        SUM(SALARY)
----------  -----------
Teddy       20000
Paul        40000
Mark        65000
Kim         45000
James       20000
David       85000
Allen       15000


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