Question

在SQL Server 2008 R2联机丛书中，它意味着分组列的最大列大小为8060字节。

“对于不包含CUBE或ROLLUP的GROUP BY子句，group_by_expression项目的数量受GROUP BY列大小，聚合列以及查询中涉及的聚合值的限制。此限制源自限制保存中间查询结果所需的中间工作表上的8,060个字节。“

但可以按varbinary（max）列进行分组：

create table dbo.T(
  name varchar(100),
  info varbinary(max)
);
insert into dbo.T values ('aardvark', Convert(varbinary(max),Replicate(Convert(varchar(max),'A'),100000)))
select info, count(*) from T group by info;

以上在SQL Server 2008 R2中运行良好，可能是更高版本。我误读了在线书籍吗？有谁知道是否允许按大对象类型进行分组？我也用Google搜索了没有结果。

Answer 1

使用固定宽度数据类型时，您更有可能遇到此问题，因为它们始终存储在行中。可变长度类型可以存储在行外，并带有指向实际值的指针。

CREATE TABLE #T
  (
     C CHAR(4027) DEFAULT REPLICATE('A', 4027)
  );

INSERT INTO #T
DEFAULT VALUES;

SELECT COUNT(*)
FROM   #T T1
       CROSS JOIN #T T2
GROUP  BY T1.C,
          T2.C

查询处理器无法生成查询计划，因为工作表是必需的，其最小行大小超过允许的最大行数 8060字节。需要工作台的典型原因是GROUP BY 或查询中的ORDER BY子句。如果查询具有GROUP BY或ORDER BY子句，考虑减少字段的数量和/或大小条款。考虑使用前缀（LEFT（））或散列（CHECKSUM（））用于分组的字段或用于排序的前缀。但请注意这一点将改变查询的行为。

但以下成功。

SELECT COUNT(*)
FROM   #T T1
       CROSS JOIN #T T2
GROUP  BY CAST(T1.C AS VARCHAR(4027)),
          CAST(T2.C AS VARCHAR(4027))

您最多可以对308个varchar（max）列进行分组 - 每行只有26个字节存储在行（pointer to the value and other overhead）中。

以下内容失败

无法创建大于8078的行，该行大于允许值最大行数为8060。

但是删除任何GROUP BY列都会成功，因为8078-26小于8060.

注意：每个单独的列的值都占用10,000个字节，但这些值存储在行外，与上述计算无关。

drop TABLE #T

GO

CREATE TABLE #T
(
 C0 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C1 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C2 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C3 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C4 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C5 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C6 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C7 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C8 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C9 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C10 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C11 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C12 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C13 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C14 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C15 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C16 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C17 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C18 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C19 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C20 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C21 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C22 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C23 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C24 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C25 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C26 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C27 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C28 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C29 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C30 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C31 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C32 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C33 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C34 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C35 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C36 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C37 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C38 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C39 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C40 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C41 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C42 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C43 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C44 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C45 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C46 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C47 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C48 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C49 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C50 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C51 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C52 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C53 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C54 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C55 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C56 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C57 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C58 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C59 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C60 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C61 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C62 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C63 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C64 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C65 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C66 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C67 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C68 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C69 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C70 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C71 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C72 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C73 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C74 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C75 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C76 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C77 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C78 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C79 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C80 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C81 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C82 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C83 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C84 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C85 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C86 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C87 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C88 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C89 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C90 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C91 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C92 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C93 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C94 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C95 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C96 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C97 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C98 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
,C99 VARCHAR(MAX) DEFAULT REPLICATE(CAST('X' AS VARCHAR(MAX)),10000)
)


INSERT INTO #T DEFAULT VALUES


SELECT COUNT(*)
FROM #T T1,
     #T T2,
     #T T3,
     #T T4
GROUP BY 
 T1.C0
,T1.C1
,T1.C2
,T1.C3
,T1.C4
,T1.C5
,T1.C6
,T1.C7
,T1.C8
,T1.C9
,T1.C10
,T1.C11
,T1.C12
,T1.C13
,T1.C14
,T1.C15
,T1.C16
,T1.C17
,T1.C18
,T1.C19
,T1.C20
,T1.C21
,T1.C22
,T1.C23
,T1.C24
,T1.C25
,T1.C26
,T1.C27
,T1.C28
,T1.C29
,T1.C30
,T1.C31
,T1.C32
,T1.C33
,T1.C34
,T1.C35
,T1.C36
,T1.C37
,T1.C38
,T1.C39
,T1.C40
,T1.C41
,T1.C42
,T1.C43
,T1.C44
,T1.C45
,T1.C46
,T1.C47
,T1.C48
,T1.C49
,T1.C50
,T1.C51
,T1.C52
,T1.C53
,T1.C54
,T1.C55
,T1.C56
,T1.C57
,T1.C58
,T1.C59
,T1.C60
,T1.C61
,T1.C62
,T1.C63
,T1.C64
,T1.C65
,T1.C66
,T1.C67
,T1.C68
,T1.C69
,T1.C70
,T1.C71
,T1.C72
,T1.C73
,T1.C74
,T1.C75
,T1.C76
,T1.C77
,T1.C78
,T1.C79
,T1.C80
,T1.C81
,T1.C82
,T1.C83
,T1.C84
,T1.C85
,T1.C86
,T1.C87
,T1.C88
,T1.C89
,T1.C90
,T1.C91
,T1.C92
,T1.C93
,T1.C94
,T1.C95
,T1.C96
,T1.C97
,T1.C98
,T1.C99

,T2.C0
,T2.C1
,T2.C2
,T2.C3
,T2.C4
,T2.C5
,T2.C6
,T2.C7
,T2.C8
,T2.C9
,T2.C10
,T2.C11
,T2.C12
,T2.C13
,T2.C14
,T2.C15
,T2.C16
,T2.C17
,T2.C18
,T2.C19
,T2.C20
,T2.C21
,T2.C22
,T2.C23
,T2.C24
,T2.C25
,T2.C26
,T2.C27
,T2.C28
,T2.C29
,T2.C30
,T2.C31
,T2.C32
,T2.C33
,T2.C34
,T2.C35
,T2.C36
,T2.C37
,T2.C38
,T2.C39
,T2.C40
,T2.C41
,T2.C42
,T2.C43
,T2.C44
,T2.C45
,T2.C46
,T2.C47
,T2.C48
,T2.C49
,T2.C50
,T2.C51
,T2.C52
,T2.C53
,T2.C54
,T2.C55
,T2.C56
,T2.C57
,T2.C58
,T2.C59
,T2.C60
,T2.C61
,T2.C62
,T2.C63
,T2.C64
,T2.C65
,T2.C66
,T2.C67
,T2.C68
,T2.C69
,T2.C70
,T2.C71
,T2.C72
,T2.C73
,T2.C74
,T2.C75
,T2.C76
,T2.C77
,T2.C78
,T2.C79
,T2.C80
,T2.C81
,T2.C82
,T2.C83
,T2.C84
,T2.C85
,T2.C86
,T2.C87
,T2.C88
,T2.C89
,T2.C90
,T2.C91
,T2.C92
,T2.C93
,T2.C94
,T2.C95
,T2.C96
,T2.C97
,T2.C98
,T2.C99


,T3.C0
,T3.C1
,T3.C2
,T3.C3
,T3.C4
,T3.C5
,T3.C6
,T3.C7
,T3.C8
,T3.C9
,T3.C10
,T3.C11
,T3.C12
,T3.C13
,T3.C14
,T3.C15
,T3.C16
,T3.C17
,T3.C18
,T3.C19
,T3.C20
,T3.C21
,T3.C22
,T3.C23
,T3.C24
,T3.C25
,T3.C26
,T3.C27
,T3.C28
,T3.C29
,T3.C30
,T3.C31
,T3.C32
,T3.C33
,T3.C34
,T3.C35
,T3.C36
,T3.C37
,T3.C38
,T3.C39
,T3.C40
,T3.C41
,T3.C42
,T3.C43
,T3.C44
,T3.C45
,T3.C46
,T3.C47
,T3.C48
,T3.C49
,T3.C50
,T3.C51
,T3.C52
,T3.C53
,T3.C54
,T3.C55
,T3.C56
,T3.C57
,T3.C58
,T3.C59
,T3.C60
,T3.C61
,T3.C62
,T3.C63
,T3.C64
,T3.C65
,T3.C66
,T3.C67
,T3.C68
,T3.C69
,T3.C70
,T3.C71
,T3.C72
,T3.C73
,T3.C74
,T3.C75
,T3.C76
,T3.C77
,T3.C78
,T3.C79
,T3.C80
,T3.C81
,T3.C82
,T3.C83
,T3.C84
,T3.C85
,T3.C86
,T3.C87
,T3.C88
,T3.C89
,T3.C90
,T3.C91
,T3.C92
,T3.C93
,T3.C94
,T3.C95
,T3.C96
,T3.C97
,T3.C98
,T3.C99
,T4.C0
,T4.C1
,T4.C2
,T4.C3
,T4.C4
,T4.C5
,T4.C6
,T4.C7
,T4.C8

分组由SQL Server中的varbinary（MAX）或varchar（MAX）组成

1 个答案: