calculate sum based on column name
Is there anyway to link one value to another based on it's column name? For e.g. in the following non-normalized table, I need to consider the value from the column state_amt_1 from another table if the state_cd_1 is 'TX' and add that value to the state_amt_2 if the state_cd_2 is 'TX' as well.
create table states (state_id int not null auto_increment, state_cd_1 varchar(100), state_cd_2 varchar(100), state_cd_3 varchar(100), state_cd_4 varchar(100), state_cd_5 varchar(100), primary key (state_id));
insert into states values (NULL, 'TX', NULL, NULL, NULL , 'OR');
insert into states values (NULL, 'OR', 'UT', NULL, NULL , NULL);
insert into states values (NULL, 'AZ', 'OR', 'UT', NULL , 'AZ');
create table amount (amt_id int not null auto_increment, state_amt_1 varchar(100), state_amt_2 varchar(100), state_amt_3 varchar(100), state_amt_4 varchar(100), state_amt_5 varchar(100), primary key (amt_id));
insert into amount values (NULL, '100', 900, NULL, NULL , '200');
insert into amount values (NULL, '250', '300', NULL, NULL , NULL);
insert into amount values (NULL, '400', '290', '350', NULL , '450');
(11:34) mysql>select * from states;
+----------+------------+-----开发者_运维知识库-------+------------+------------+------------+
| state_id | state_cd_1 | state_cd_2 | state_cd_3 | state_cd_4 | state_cd_5 |
+----------+------------+------------+------------+------------+------------+
| 1 | TX | NULL | NULL | NULL | OR |
| 2 | OR | UT | NULL | NULL | NULL |
| 3 | AZ | OR | UT | NULL | AZ |
+----------+------------+------------+------------+------------+------------+
(11:34) mysql>select * from amount;
+--------+-------------+-------------+-------------+-------------+-------------+
| amt_id | state_amt_1 | state_amt_2 | state_amt_3 | state_amt_4 | state_amt_5 |
+--------+-------------+-------------+-------------+-------------+-------------+
| 1 | 100 | 900 | NULL | NULL | 200 |
| 2 | 250 | 300 | NULL | NULL | NULL |
| 3 | 400 | 290 | 350 | NULL | 450 |
+--------+-------------+-------------+-------------+-------------+-------------+
Expected result:
TX 100
OR 740
UT 650
AZ 850
OR
TX OR UT AZ
100 740 650 850
How to calculate:
TX: 100
OR: 200+250+290=740
UT: 300+350=650
AZ: 400+450=850
Note: The names of states may change.
It's ugly, but you can do it with unions like this:
SELECT st, sum(amt) FROM (
(
SELECT s.state_cd_1 AS st, a.state_amt_1 AS amt
FROM states AS s JOIN amount AS a ON s.state_id = a.amt_id
WHERE s.state_cd_1 IS NOT NULL AND a.state_amt_1 IS NOT NULL
) UNION ALL (
SELECT s.state_cd_2 AS st, a.state_amt_2 AS amt
FROM states AS s JOIN amount AS a ON s.state_id = a.amt_id
WHERE s.state_cd_2 IS NOT NULL AND a.state_amt_2 IS NOT NULL
) UNION ALL (
SELECT s.state_cd_3 AS st, a.state_amt_3 AS amt
FROM states AS s JOIN amount AS a ON s.state_id = a.amt_id
WHERE s.state_cd_3 IS NOT NULL AND a.state_amt_3 IS NOT NULL
) UNION ALL (
SELECT s.state_cd_4 AS st, a.state_amt_4 AS amt
FROM states AS s JOIN amount AS a ON s.state_id = a.amt_id
WHERE s.state_cd_4 IS NOT NULL AND a.state_amt_4 IS NOT NULL
) UNION ALL (
SELECT s.state_cd_5 AS st, a.state_amt_5 AS amt
FROM states AS s JOIN amount AS a ON s.state_id = a.amt_id
WHERE s.state_cd_5 IS NOT NULL AND a.state_amt_5 IS NOT NULL
)) AS joined GROUP BY st;
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