MySQL calculating query - mysql

Question

I have this table, only two columns, each record stores an interest rate for a given month:
id rate
===========
199502 3.63
199503 2.60
199504 4.26
199505 4.25
... ...
201704 0.79
201705 0.93
201706 0.81
201707 0.80
201708 0.14
Based on this rates, I need to create another table of accumulated rates which similar structure, whose data is calculated as function of a YYYYMM (month/year) parameter, this way (this formula is legally mandatory):
The month given as parameter has always rate of 0 (zero)
The month immediately previous has always a rate of 1 (one)
The previous months' rates will be (one) plus the sum of rates of months between that given month and the month given as parameter.
I'll clarify this rules with this example, given parameter 201708:
SOURCE CALCULATED
id rate id rate
=========== =============
199502 3.63 199502 360.97 (1 + sum(rate(199503) to rate(201707)))
199503 2.60 199503 358.37 (1 + sum(rate(199504) to rate(201707)))
199504 4.26 199504 354.11 (1 + sum(rate(199505) to rate(201707)))
199505 4.25 199505 349.86 (1 + sum(rate(199506) to rate(201707)))
... ... ... ...
201704 0.79 201704 3.54 (1 + rate(201705) + rate(201706) + rate(201707))
201705 0.93 201705 2.61 (1 + rate(201706) + rate(201707))
201706 0.81 201706 1.80 (1 + rate(201707))
201707 0.80 201707 1.00 (per definition)
201708 0.14 201708 0.00 (per definition)
Now I've already implemented a VB.NET function that reads the source table and generates the calculated table, but this is done in runtime at each client machine:
Public Function AccumRates(targetDate As Date) As DataTable
Dim dtTarget = Rates.Clone
Dim targetId = targetDate.ToString("yyyyMM")
Dim targetIdAnt = targetDate.AddMonths(-1).ToString("yyyyMM")
For Each dr In Rates.Select("id<=" & targetId & " and id>199412")
If dr("id") = targetId Then
dtTarget.Rows.Add(dr("id"), 0)
ElseIf dr("id") = targetIdAnt Then
dtTarget.Rows.Add(dr("id"), 1)
Else
Dim intermediates =
Rates.Select("id>" & dr("id") & " and id<" & targetId).Select(
Function(ldr) New With {
.id = ldr.Field(Of Integer)("id"),
.rate = ldr.Field(Of Decimal)("rate")}
).ToArray
dtTarget.Rows.Add(
dr("id"),
1 + intermediates.Sum(
Function(i) i.rate))
End If
Next
Return dtTarget
End Function
My question is how can I put this as a query in my database so it can be used dynamically by other queries which would use these accumulated rates to update debts to any given date.
Thank you very much!
EDIT
I managed to make a query that returns the data I want, now I just don't know how to encapsulate it so that it can be called from another query passing any id as argument (here I did it using a SET ... statement):
SET #targetId=201708;
SELECT
id AS id_acum,
COALESCE(1 + (SELECT
SUM(taxa)
FROM
tableSelic AS ts
WHERE
id > id_acum AND id < #targetId
LIMIT 1),
IF(id >= #targetId, 0, 1)) AS acum
FROM
tableSelic
WHERE id>199412;
That's because I'm pretty new to MySQL, I'm used to MS-Access where parametrized queries are very straightfoward to create.

Answer 1

For example:
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(id INT NOT NULL PRIMARY KEY
,rate DECIMAL(5,2) NOT NULL
);
INSERT INTO my_table VALUES
(201704,0.79),
(201705,0.93),
(201706,0.81),
(201707,0.80),
(201708,0.14);
SELECT *
, CASE WHEN #flag IS NULL THEN #i:=1 ELSE #i:=#i+rate END i
, #flag:=1 flag
FROM my_table
, (SELECT #flag:=null,#i:=0) vars
ORDER
BY id DESC;
+--------+------+-------------+-------+------+------+
| id | rate | #flag:=null | #i:=0 | i | flag |
+--------+------+-------------+-------+------+------+
| 201708 | 0.14 | NULL | 0 | 1 | 1 |
| 201707 | 0.80 | NULL | 0 | 1.80 | 1 |
| 201706 | 0.81 | NULL | 0 | 2.61 | 1 |
| 201705 | 0.93 | NULL | 0 | 3.54 | 1 |
| 201704 | 0.79 | NULL | 0 | 4.33 | 1 |
+--------+------+-------------+-------+------+------+
5 rows in set (0.00 sec)

Answer 2

Ok, I made it with a function:
CREATE FUNCTION `AccumulatedRates`(start_id integer, target_id integer) RETURNS decimal(6,2)
BEGIN
DECLARE select_var decimal(6,2);
SET select_var = (
SELECT COALESCE(1 + (
SELECT SUM(rate)
FROM tableRates
WHERE id > start_id AND id < target_id LIMIT 1
), IF(id >= unto, 0, 1)) AS acum
FROM tableRates
WHERE id=start_id);
RETURN select_var;
END
And them a simple query:
SELECT *, AccumulatedRates(id,#present_id) as acum FROM tableRates;
where #present_id is passed as parameter.
Thanks to all, anyway!