dividing sum of the column with each part - sql

Question

i have the following table in my database
i am currently using oracle 11g
the data is like this
id valus
1 2 3
100 200 300 = 600
I want to derive new column as: divide each value from the column "value" with the total sum of the column "value". Then load into the another table. The data in other table should look as
id value drived_col
1 100 100/600
2 200 200/600
3 300 300/600
thanks

Answer 1

SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE data ( id, value ) AS
SELECT 1, 100 FROM DUAL
UNION ALL SELECT 2, 200 FROM DUAL
UNION ALL SELECT 3, 300 FROM DUAL;
CREATE TABLE derived_data AS
SELECT id,
value,
value/SUM(value) OVER ( ORDER BY NULL ) AS derived_col
FROM data;
Or if the derived_data table already exists then you can do:
INSERT INTO derived_data
SELECT id,
value,
value/SUM(value) OVER ( ORDER BY NULL ) AS derived_col
FROM data;
Query 1:
SELECT * FROM derived_data
Results:
| ID | VALUE | DERIVED_COL |
|----|-------|----------------|
| 1 | 100 | 0.166666666667 |
| 2 | 200 | 0.333333333333 |
| 3 | 300 | 0.5 |
Or if you want the derived_col as a string:
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE data ( id, value ) AS
SELECT 1, 100 FROM DUAL
UNION ALL SELECT 2, 200 FROM DUAL
UNION ALL SELECT 3, 300 FROM DUAL;
CREATE TABLE derived_data AS
SELECT id,
value,
value||'/'||SUM(value) OVER ( ORDER BY NULL ) AS derived_col
FROM data;
Query 1:
SELECT * FROM derived_data
Results:
| ID | VALUE | DERIVED_COL |
|----|-------|-------------|
| 1 | 100 | 100/600 |
| 2 | 200 | 200/600 |
| 3 | 300 | 300/600 |

Answer 2

Assuming your table already exists, you want to use an INSERT INTO new_table SELECT to insert the data in the derived table based on a query. For the insertion query to perform the division, it needs two subqueries:
query the sum of the values
query the (id,value) pair
Because the sum of the values is a single value, constant for all rows, you can then join these subqueries together with an INNER JOIN that has no conditions:
INSERT INTO derived_table
SELECT
ot.id AS id,
ot.value AS value,
CAST(ot.value AS float)/summed.total AS derived_col
FROM
orig_table AS ot
INNER JOIN
SELECT sum(value) AS total FROM orig_table AS summed;
The CAST(ot.value AS FLOAT) is necessary if value is a column of integers. Otherwise, your division will be integer division and all of the derived values will be zero.
There is no join condition here because the summation is a single value to all rows of orig_table. If you want to apply different divisors to different rows, you would need a more complicated subquery and an appropriate join condition.