SQL查找带有条件列的表

Question

I'm looking for a way to use a 'lookup' table to get the color values. See my examples below of the two tables and results in looking for.

Table columns and values:

ColumnName |   Condition       | CellColor
Rank       |   > 90            | Green
Rank       | between 70 and 89 | Yellow
Rank       |   < 70            | Red
Score      |   > 89            | Purple
Score      |   < 88            | Orange

Personnel Table

Name | Rank | Score
Jane | 100  | 50
John | 77   | 90
Kelly| 50   | 99

Results I want to get

PersonnelName | Rank | RankCellColor | Score | Scoredcolor
Jane          | 100  |    Green      |  50   |  Orange
John          | 77   |   Yellow      |  90   |  Purple
Kelly         | 50   |    Red        |  99   | Purple

I've tried to loop through the columns Rank and Score, but get stuck on how to use the condition. I get lost in coding this. I really need help in figuring this out.

Any help would be appreciated!!

Answer 1

SQL is not suited to this type of problem. You could structure the conditions table as:

ColumnName, Lower, Upper, CellColor
Rank, 90, NULL, Green
Rank, 70,  89, Yellow
Rank, NULL, 70, Red
Score, 89, NULL, Purple
Score, NULL, 88, Orange

Then your query would look like:

select p.*, cr.color as rankcolor, cs.color as scorecolor
from personnel p left join
     conditions c
     on cr.columnname = 'Rank' and
        (p.rank >= cr.lower or cr.lower is null) and
        (p.rank <= cr.upper or cr.upper is null) left join
     conditions cs
     on cs.columnname = 'Score' and
        (p.score >= cs.lower or cs.lower is null) and
        (p.score <= cs.upper or cs.upper is null);

Answer 2

If you specify lower and upper limits for the color this will be much easier. You can join the table where the values fall within the ranges of the lower and upper limits.

CREATE TABLE Conditions (ColumnName varchar(50), minval int, maxval int, CellColor varchar(50))
INSERT INTO Conditions
VALUES
 ('Rank', 90, 100, 'Green')
,('Rank', 70, 89, 'Yellow')
,('Rank', 0, 70, 'Red')
,('Score', 89, 100, 'Purple')
,('Score', 0, 88, 'Orange')

CREATE TABLE Personnel (Name varchar(50), Rank int, Score int)

INSERT INTO Personnel 
VALUES
 ('Jane', 100, 50)
,('John', 77, 90)
,('Kelly', 50, 99)

SELECT P.Name, P.Rank, ConRank.CellColor, P.Score, ConScore.CellColor
  FROM Personnel P 
       INNER JOIN Conditions ConRank 
        ON P.Rank >= ConRank.minval AND P.Rank <= ConRank.maxval AND ConRank.ColumnName = 'Rank'
       INNER JOIN Conditions ConScore
        ON P.Score >= ConScore.minval AND P.Score <= ConScore.maxval AND ConScore.ColumnName = 'Score'
ORDER BY P.Name   

Gives output:

Name    Rank    CellColor   Score   CellColor
Jane    100     Green       50      Orange
John    77      Yellow      90      Purple
Kelly   50      Red         99      Purple

Reference this sqlfiddle: http://sqlfiddle.com/#!6/15f3a/6