SQL错误: ORA-00936:缺少表达式

Question

你能告诉我sql中的错误是什么吗？我遇到了缺少表达式的错误，但我找不到错误。非常提前感谢您。

SELECT SYSTEMNAME, round(MAX(GBL_CPU_TOTAL_UTIL),2) AS AVE_CPU,
convert(varchar(20),DATEADD(hour, DATEDIFF(hour, 0, DATETIME), 0),110) AS DATE
FROM dbo.[GLOBAL]
WHERE (SYSTEMNAME IN ( 'X1','X2','X3'))    
AND (DATETIME > DATEADD(month, - 24, GETDATE()))
AND (DATETIME BETWEEN '12-27-2011 00:00' AND '12-30-2011 00:00')
GROUP BY SYSTEMNAME, convert(varchar(20),
DATEADD(hour, DATEDIFF(hour, 0, DATETIME), 0),110)
ORDER BY DATE

错误：

ORA-00936: missing expression
00936. 00000 -  "missing expression"
*Cause:    
*Action:
Error at Line: 2 Column: 9

Answer 1

convert(varchar(20), ...？

据我所知，convert用于将字符串从一个字符集转换为另一个字符集。varchar(20)不是字符串。情况也很可能是这样，因为“第2行，第9列”正是varchar(20)所在的位置。

convert的文档说明：

convert( string1 , char_set_to , [ char_set_from ] )

string1 is the string to be converted.

char_set_to is the character set to convert to.

char_set_from is the character set to convert from.

如果您打算将日期差异转换为varchar(20)类型，则可能应该使用cast。