How can we use MySQL SUM() function to calculate the sum of distinct values ​​in a column?

To calculate the sum of distinct values ​​in a column, we can use the "DISTINCT" keyword with the column name. To understand the SUM() function for different values, consider an "employee_tbl" table which has the following records -

mysql> SELECT * FROM employee_tbl;
+------+------+------------+--------------------+
| id   | name | work_date  | daily_typing_pages |
+------+------+------------+--------------------+
| 1    | John | 2007-01-24 | 250                |
| 2    | Ram  | 2007-05-27 | 220                |
| 3    | Jack | 2007-05-06 | 170                |
| 3    | Jack | 2007-04-06 | 100                |
| 4    | Jill | 2007-04-06 | 220                |
| 5    | Zara | 2007-06-06 | 300                |
| 5    | Zara | 2007-02-06 | 350                |
+------+------+------------+--------------------+
7 rows in set (0.00 sec)

Now, suppose you want to calculate the sum of all dialy_typing_pages with different values ​​based on the above table, Then you can do it using the following command -

mysql> SELECT SUM(DISTINCT daily_typing_pages)
    -> FROM employee_tbl;
+-------------------------+
| SUM(daily_typing_pages) |
+-------------------------+
|       1390              |
+-------------------------+
1 row in set (0.00 sec)

The above result set shows that MySQL SUM() with DISTINCT keyword only calculates the sum of distinct records, i.e. only adds the value "220" once.

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