How to Divide Sum in Number from Count in Having

Dividing a SUM with a Count returns false results

You forgot to join your tables.

Try this:

SELECT SUM(ACCOUNT_COUNT) / COUNT(IS_TERMINATED) 
FROM T_APPLICATIONS x inner join V_USERS v ON x.ID = v.ID
 WHERE RESOURCE_TYPE='A';

And if you dont have a key to join then try this:

SELECT
  (SELECT SUM(ACCOUNT_COUNT) FROM T_APPLICATIONS WHERE RESOURCE_TYPE='A') /
  (SELECT COUNT(IS_TERMINATED) FROM V_USERS)

MySQL Percentage Divide count by sum

As I was indicating in my comment, both parts do not need to be subqueries.

  SELECT name
     , COUNT(*) AS total
     , 100 * COUNT(*)/s.total_sum AS percentage
  FROM games 
  CROSS JOIN (
     SELECT COUNT(*) AS total_sum 
     FROM games 
     WHERE gameStatus = 'win' 
       AND created_at > '2018-03-01 12:02:26'
  ) AS s
  WHERE gameStatus = 'win' 
    AND created_at > '2018-03-01 12:02:26'
  GROUP BY name
  ;

Not sure if this will actually be any faster though; I wouldn't be surprised if MySQL ends up handling them in nearly identical manners.

Divide count by count(*) in SQL Server

Instead of

COUNT(CASE WHEN t.id is null THEN 1 END)/Count(*)

You can use

AVG(CASE WHEN t.id is null THEN 1.0 ELSE 0 END)

Dividing SUM By A Distinct Count and getting an error

Move the subquery to the FROM clause:

SELECT SUM(DISTINCT CE.USD_NOTIONAL) / MAX(dey.cntd)
FROM CE CROSS JOIN
     (SELECT COUNT(DISTINCT MARKET_DATE) as cntd
      FROM DATA_EURO_YTD
      WHERE MARKET_DATE >= DATE '2019-01-01'
     )   dey
WHERE CE.tradedate >= DATE '2019-01-01'  AND
      CE.exchange IN (SELECT EXCHANGE
                      FROM exchange EX
                      WHERE EX.FEED IN ('Y')
                     );

Notes:

Moving the subquery to the FROM clause almost solves the whole problem. You still need an aggregation around the value.
SELECT DISTINCT is redundant in an IN subquery.
I fixed the dates to use the DATE prefix for date literals.

SQL SUM values from column and dividide by number of rows

use COUNT to get the totalNumber of rows.

SELECT SUM(voto) / (COUNT(*) * 1.0) 
FROM   tablename 
WHERE  id = numberHere

by adding * 1.0 on the query will allow decimal places on the result.

or simply as

SELECT AVG(voto)
FROM   tablename 
WHERE  id = numberHere