MySQL Case/If/Then

Question

I am trying to build a query in MySQL, where I have a numeric stock level of something and depending on what that stock level is, I want it to return another value that woul

Answer 1

I thin you mean that if the stock > 1000 then another color not green.

SELECT  Beer.Beer, 
        Beer.Brewery, 
        Beer.Style, 
        Beer.ABV, 
        Beer.Hops, 
        Beer.SRM,
        Sum(BeerStock.Quantity) totalQuantity,
        CASE WHEN Sum(BeerStock.Quantity) < 0 THEN ''
            WHEN Sum(BeerStock.Quantity) BETWEEN 0 AND 999 THEN 'Red'
            WHEN Sum(BeerStock.Quantity) BETWEEN 1000 AND 4999 THEN 'Yellow'
            WHEN Sum(BeerStock.Quantity) BETWEEN 5000 AND 9999 THEN 'GREEN'
            WHEN Sum(BeerStock.Quantity) >= 10000 THEN 'Another Color' 
        END
FROM    Beer
        INNER JOIN BeerStock
            ON Beer.Beer = BeerStock.Beer
-- Where    ..other conditions..

but if you really mean that,

SELECT  Beer.Beer, 
        Beer.Brewery, 
        Beer.Style, 
        Beer.ABV, 
        Beer.Hops, 
        Beer.SRM,
        Sum(BeerStock.Quantity) totalQuantity,
        CASE WHEN Sum(BeerStock.Quantity) < 0 THEN ''
            WHEN Sum(BeerStock.Quantity) BETWEEN 0 AND 999 THEN 'Red'
            WHEN Sum(BeerStock.Quantity) BETWEEN 1000 AND 4999 THEN 'Yellow'
            WHEN Sum(BeerStock.Quantity) >= 5000 THEN 'GREEN'
        END
FROM    Beer
        INNER JOIN BeerStock
            ON Beer.Beer = BeerStock.Beer
-- Where    ..other conditions..

---

One more thing, You also need to use GROUP BY clause or else you will be returning only one record even if you have different records,

SELECT  Beer.Beer, 
        Beer.Brewery, 
        Beer.Style, 
        Beer.ABV, 
        Beer.Hops, 
        Beer.SRM,
        Sum(BeerStock.Quantity) totalQuantity,
        CASE WHEN Sum(BeerStock.Quantity) < 0 THEN ''
            WHEN Sum(BeerStock.Quantity) BETWEEN 0 AND 999 THEN 'Red'
            WHEN Sum(BeerStock.Quantity) BETWEEN 1000 AND 4999 THEN 'Yellow'
            WHEN Sum(BeerStock.Quantity) BETWEEN 5000 AND 9999 THEN 'GREEN'
            WHEN Sum(BeerStock.Quantity) >= 10000 THEN 'Another Color' 
        END
FROM    Beer
        INNER JOIN BeerStock
            ON Beer.Beer = BeerStock.Beer
-- Where    ..other conditions..
GROUP   BY Beer.Beer, 
        Beer.Brewery, 
        Beer.Style, 
        Beer.ABV, 
        Beer.Hops, 
        Beer.SRM

Answer 2

Something like this should work using the CASE statement:

SELECT Beer, Brewery, Style, ABV, SRM, SummedQty, 
    CASE 
       WHEN SummedQty >=0 AND SummedQty <= 1000 THEN ' RED'
       WHEN SummedQty >1000 AND SummedQty <= 5000 THEN ' YELLOW'
       WHEN SummedQty >5000 THEN ' GREEN'
       ELSE ''
    END yourcolor
FROM (
    SELECT Beer.Beer, Beer.Brewery, Beer.Style, Beer.ABV, Beer.Hops, Beer.SRM,
       Sum(BeerStock.Quantity) SummedQty
    FROM Beer
       INNER JOIN BeerStock  
          ON Beer.Beer = BeerStock.Beer
    ) t

Be careful using BETWEEN -- it may not return your desired results. I prefer using greater than and less than. I also converted your JOIN syntax to an INNER JOIN.