Sql 在Postgres中获得4位小数

我正在尝试运行以下查询：

SELECT questionid,
       (SUM(CASE WHEN correct = FALSE THEN 1 ELSE 0 END)::decimal(10,4) / COUNT(*)::decimal(10,4))::decimal(10,4) AS PercentWrong,
       COUNT(questionid) AS Questions
FROM asmt.testscores
WHERE testscoreid IN (SELECT DISTINCT test_score_id
                      FROM ads.fbs_assessment_adaptive_pause_staging)
AND   answered = TRUE
AND   memberid IS NOT NULL
GROUP BY questionid
ORDER BY PercentWrong

我希望列

percenterror

有4位小数，但是上面的查询只给了我2位小数，尽管有

decimal（10,4）

。我也试着使用

real

，但它根本没有给我小数点

如何获取小数点后4位？

尝试使用

试用

SELECT questionid,
       to_char(SUM(CASE WHEN correct = FALSE THEN 1 ELSE 0 END)::float / COUNT(*)::float,'99D9999') AS PercentWrong,
       COUNT(questionid) AS Questions
FROM asmt.testscores
WHERE testscoreid IN (SELECT DISTINCT test_score_id
                      FROM ads.fbs_assessment_adaptive_pause_staging)
AND   answered = TRUE
AND   memberid IS NOT NULL
GROUP BY questionid
ORDER BY PercentWrong