Sql server SQL查询和别名问题

有人能告诉我为什么这是抱怨吗？ 我使用的是SQL Server，其中一个表名为test，一个列名为word

这是我的疑问：

SELECT TOP 1
COUNT(*) AS count, 
(LEN(word) - LEN(REPLACE(word,'A',''))) AS letters
FROM dbo.TEST 
WHERE 
word LIKE '******' 
GROUP BY letters 
ORDER BY count DESC

这是结果错误：

Msg 207, Level 16, State 1, Line 7
Invalid column name 'letters'.

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为什么抱怨我的别名？

您不能在组中使用别名，请使用相同的计算列：

SELECT TOP 1
COUNT(*) AS count, 
(LEN(word) - LEN(REPLACE(word,'A',''))) AS letters
FROM dbo.TEST 
WHERE 
word LIKE '******' 
GROUP BY (LEN(word) - LEN(REPLACE(word,'A','')))
ORDER BY count DESC

---

不能在GROUP BY子句中使用别名。 这是由于SQL处理顺序，在选择之前先处理GROUP BY。 尝试替换：

GROUP BY letters

与

---

不能在查询中使用别名。您需要的是：

SELECT TOP 1
COUNT(*) AS count, 
(LEN(word) - LEN(REPLACE(word,'A',''))) AS letters
FROM dbo.TEST 
WHERE 
word LIKE '******' 
GROUP BY (LEN(word) - LEN(REPLACE(word,'A','')))
ORDER BY count DESC

---

希望这有助于在查询中更改组

   SELECT TOP 1
            COUNT(*) AS count ,
            ( LEN(word) - LEN(REPLACE(word, 'A', '')) ) AS letters
    FROM    dbo.TEST
    WHERE   word LIKE '******'
    GROUP BY ( LEN(word) - LEN(REPLACE(word, 'A', '')) )
    ORDER BY count DESC

看<代码>分组依据运行第五<代码>选择第八次运行。和“因为SELECT子句是步骤8，所以前面的子句不能引用该子句中定义的任何列别名或派生列”

   SELECT TOP 1
            COUNT(*) AS count ,
            ( LEN(word) - LEN(REPLACE(word, 'A', '')) ) AS letters
    FROM    dbo.TEST
    WHERE   word LIKE '******'
    GROUP BY ( LEN(word) - LEN(REPLACE(word, 'A', '')) )
    ORDER BY count DESC