除法结果为零时返回字符串

Question

I have an SQL query like this:

SELECT 
u.id,
tu.score/(CASE tu.mo_count  WHEN 0 THEN NULL ELSE tu.mo_count END) AS score_avg
FROM tournament_userscore tu
INNER JOIN users u ON u.id = tu.user_id
WHERE tournament_id = 1
ORDER BY tu.score DESC

When tu.mo_count is zero, Null has been replaced instead of zero. How can I set a string like 'EMPTY' for this line:

tu.score/(CASE tu.mo_count  WHEN 0 THEN NULL ELSE tu.mo_count END) AS score_avg

I mean when division result is zero or empty , I want to return " anything " string.

Answer 1

You could use NULLIF and COALESCE if you don't want to use a CASE:

SELECT 
  u.id,
  COALESCE(tu.score/NULLIF(tu.mo_count, 0), 0) AS score_avg
FROM tournament_userscore tu
  INNER JOIN users u ON u.id = tu.user_id
WHERE 
  tournament_id = 1
ORDER BY 
  tu.score DESC;

Answer 2

Try moving the CASE -statement outside:

SELECT 
u.id,
CASE WHEN tu.mo_count = 0 THEN 'EMPTY' ELSE (tu.score/tu.mo_count)::text END as score_avg
FROM tournament_userscore tu
INNER JOIN users u ON u.id = tu.user_id
WHERE tournament_id = 1
ORDER BY tu.score DESC