我想计算 PostgreSQL 中某一列的平均数
SELECT AVG(col_name)
From TableName
它给了我这个错误:
ERROR: function avg (character varying) does not exist
LINE 1: SELECT AVG(col_name)
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
将数字存储在数字字段中,可以是整数、小数或其他形式。但不在 text/varchar 字段中。
全部查看说明书数字数据类型.
讨厌的解决方法:将一些记录转换为数值,并将其他记录保留为文本。例子:
/*
create temp table foo AS
SELECT x FROM (VALUES('x'),('1'),('2')) sub(x);
*/
WITH cte AS (
SELECT
CASE
WHEN x ~ '[0-9]' THEN CAST(x AS decimal) -- cast to numeric field
END AS num,
CASE
WHEN x ~ '[a-zA-Z]' THEN x
END AS a
FROM foo
)
SELECT AVG(num), COUNT(a) FROM cte;
本文内容由网友自发贡献,版权归原作者所有,本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容,请联系:hwhale#tublm.com(使用前将#替换为@)