i have a simple table . How can i sum in SQL only values based on Riclass ID?

I tried this code but doesn't work.

SELECT 
Riclass_ID
SUM (Value)
FROM Mytable
WHERE Riclass_Id= 0 and Riclass_Id= 3

CodePudding user response：

Drop Riclass_ID from Select

SELECT SUM (Value)
  FROM Mytable
 WHERE Riclass_Id in (0, 3)

and you'll get a single record - sum of all Values which belong to records with Riclass_Id equals to either 0 or 3

CodePudding user response：

If you want the sum by Riclass_ID you need use group by clause : choose fields to be grouped

If you want only some Riclass_ID, you need use where clause : choose the value to be filtered

With group by clause, you can select only :

• aggregat function (here SUM(value), or count(*), or min/max...)
• fields specify in group by
• const

With one (or more) aggregat function in the selectclause AND without group by clause, you can't select fields without aggregat.

SELECT 
    Riclass_ID,
    SUM (Value)
FROM
    Mytable
WHERE
    Riclass_Id in (0,3)
GROUP BY 
    Riclass_Id