Apply a function for all columns of a table - mysql

Question

I am trying to make a calculation in MySQL for all columns of a table.
Table: bev
Jahr GKZ gesamt A B C
2017 1111000 88.519 855 888 814
2017 1112000 247.943 2.414 2.379 2.262
2017 1113000 253.106 2.290 2.343 2.289
2017 1113004 43.392 408 416 403
2017 1113008 12.383 137 134 124
2017 1113012 27.106 252 252 249
2017 1113016 41.673 391 410 398
2017 1113020 39.585 364 391 373
2017 1113024 10.075 63 73 74
2017 1113028 24.083 199 205 209
2017 1113032 8.745 63 77 65
2017 1113036 18.143 170 170 143
2017 1113040 27.921 243 215 251
Table: ja
GKZ Jahr ja_name
1001000 2017 K X
1002000 2017 K Y
5370000 2017 L Z
5370004 2017 Z1
5370012 2017 Z2
5370016 2017 Z3
5370020 2017 Z4
I already got the calculation for one column (the first one: gesamt) in a function:
CREATE DEFINER=`DB`#`%` FUNCTION `Total_Amount_Funct`(
bev_ID int(11),
bev_Total int(11),
ja_name VARCHAR(255),
ja_jahr int(11)) RETURNS int(11)
DETERMINISTIC
BEGIN
DECLARE Total_Amount int(11);
DECLARE kreis int(11);
DECLARE Total_Sum int(11);
SET kreis = (bev_ID / 1000) ;
SET Total_Sum = (SELECT SUM(b.gesamt)
FROM bev as b, ja as j
WHERE b.GKZ = j.GKZ
AND b.Jahr = j.Jahr
AND j.Jahr = ja_jahr
AND (MOD(b.GKZ, 1000) <> 0)
AND (MOD(b.GKZ, 1000) != 0)
AND NOT (MOD(b.GKZ, 1000) = 0)
AND (b.GKZ BETWEEN (kreis*1000 + 1) AND (((kreis+1)*1000)-1))
AND j.ja_name IS NOT NULL);
SET Total_Amount = bev_Total-Total_Sum;
RETURN (Total_Amount);
END
This function can be called with the following select:
SELECT DISTINCT
bev.GKZ,
bev.Jahr,
bev.gesamt,
CASE WHEN (bev.GKZ % 1000 = 0) THEN
coalesce(Total_Amount_Funct(bev.GKZ, bev.gesamt, ja.ja_name, bev.Jahr), bev.gesamt)
ELSE bev.gesamt
END AS bev,
ja.ja_name
FROM
ja, bev
WHERE
bev.GKZ = ja.GKZ
AND bev.Jahr = ja.Jahr;
I really would like to apply the function for all columns of the table. Maybe as a stored procedure? Maybe as dynamic columns. I do not know. I have solved this problem in MS SQL with dynamic columns but I have the feeling that translating it will take more time than trying to complete the function as a Stored Procedure.
The name of the columns can be obtained by:
SELECT column_name
FROM information_schema.columns
WHERE table_name='bev'
and column_name not in ('Jahr','GKZ');
As Result it should be:
GKZ Jahr gesamt bev ja_name
1111000 2017 88.519 88.519 K X
1112000 2017 247.943 247.943 K Y
1113000 2017 253.106 101.350 L Z
1113004 2017 43.392 43.392 Z1
1113012 2017 27.106 27.106 Z2
1113016 2017 41.673 41.673 Z3
1113020 2017 39.585 39.585 Z4

Answer 1

As you are using the column only in the SUM, you could pass the column name as parameter and use CASE-statement to pick the column accordingly. Something like:
CREATE FUNCTION `Total_Amount_Funct`(
bev_ID decimal(8,3),
bev_Total int,
ja_name VARCHAR(255),
ja_jahr int,
in_col varchar(10)
)
RETURNS int
DETERMINISTIC
BEGIN
DECLARE Total_Amount int(11);
DECLARE Total_Sum int(11);
SELECT
SUM(
case
when in_col='gesamt' then b.gesamt
when in_col='A' then b.A
when in_col='B' then b.B
when in_col='C' then b.C
end
) into Total_Sum
FROM bev as b
join ja as j on b.GKZ = j.GKZ AND b.Jahr = j.Jahr
WHERE
MOD(b.GKZ, 1000) != 0
AND b.GKZ BETWEEN bev_ID+1 AND bev_ID+999
AND j.ja_name IS NOT NULL
SET Total_Amount = bev_Total-Total_Sum;
RETURN (Total_Amount);
END
And then call the function with column name and correct value:
Total_Amount_Funct(bev.GKZ, bev.gesamt, ja.ja_name, bev.Jahr, 'gesamt'),
Total_Amount_Funct(bev.GKZ, bev.A, ja.ja_name, bev.Jahr, 'A')
...
Note that calling a function which makes a query will serialize your SQL (calling the function on each row causes the function query to be executed on each row). This will hurt the query performance.

Answer 2

slaakso,
thank you very much for your answer. You are from today my idol :-).
Thanks Thanks.
I have maybe one performance Question.
It is posible to write the function for all columns of the table bev. We can copy the column names in a temporary table:
CREATE TEMPORARY TABLE listColumns(
Columns_ID MEDIUMINT NOT NULL AUTO_INCREMENT ,
Columnsnamen varchar(256) ,
PRIMARY KEY (Columns_ID)
);
Readed from the System Information:
insert into listColumns (Columnsnamen)
SELECT column_name
FROM information_schema.columns
WHERE table_name='bev'
and column_name not in ('Jahr','GKZ');
This Table looks like:
Columns_ID Columnsnamen
1 gesamt
2 A
3 B
4 C
5
6
In such a way, that it is not necessary to mentione every column name (the table contains about 100 columns). Maybe with a cursor over the Columns_ID?
It woul be great if you have another advice for me.
Thank you and kind regads
Ana