SQL：根据表中的值动态选择列名

Question

I a have a table name(weight) in database

id	1000	500	300	100	1
1	60	120	140	180	200

for 1000 (1kg)time required is 60

for 500 (.5kg)time required is 120 and so on

based on this weight data should be fetched from the table

If the entered weight by the user is 700 it should fetch the data of 500 which is the less than 700 and return the value 120

so my code must be like

    SELECT (column name)<700 FROM Weight WHERE id=1 

Thanks:)

Answer 1

It will be much easy if you rearrange your data like:

id, condition, value
1,  1000       60
1,  500        120
1,  300        140

and the query would be like this:

SELECT value FROM table WHERE id=1 AND condition < 700 ORDER BY condition DESC LIMIT 1

Answer 2

Your approach is not efficient to get your desired results.

Update your table:weight with the below one.

SQL:

CREATE TABLE `weight` (
  `id` int(11) NOT NULL,
  `weight` int(11) NOT NULL,
  `time` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
INSERT INTO `weight` (`id`, `weight`, `time`) VALUES
(1, 100, 60),
(2, 500, 120),
(3, 300, 140),
(4, 100, 180),
(5, 1, 200);
ALTER TABLE `weight`
  ADD PRIMARY KEY (`id`);
ALTER TABLE `weight`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=6;
COMMIT;

Add use the following query to get your desired results.

SELECT time FROM weight WHERE weight<=700 ORDER BY weight DESC LIMIT 1

Answer 3

You can use case.. when in select clause as follows:

Select case when your_value >= 1000 then column_1000
            when your_value >= 500 then column_500
            when your_value >= 300 then column_300
            when your_value >= 100 then column_100
             Else column_1 
       End as res_
  From your_table t