"String or binary data would be truncated." 适用于 NVARCHAR 但不适用于 LIKE 操作中的 VARCHAR

Question

在SQL服务器中，nvarchar占用varchar的space的两倍，与varchar相比，其前页指针限制为4000的 8000.

那么，为什么下面的like比较给出String or binary data would be truncated.错误...

select 1 where '' like cast(replicate('x', 4001) as nvarchar(max))

...而投射为更大的 varchar 不是吗？

select 1 where '' like cast(replicate('x', 123456) as varchar(max))

事实上，为什么top live在明确声明为nvarchar(max)的情况下会出现截断错误根本，其大小限制约为2GB？

Answer 1

来自 LIKE 运算符的 description：

pattern

Is the specific string of characters to search for in match_expression, and can include the following valid wildcard characters. pattern can be a maximum of 8,000 bytes.

此查询显示符号的实际计数：

select  len(replicate('x', 123456)) as  CntVarchar,
        len(replicate('x', 4001))   as  CntNVarchar


+------------+-------------+
| CntVarchar | CntNVarchar |
+------------+-------------+
|       8000 |        4001 |
+------------+-------------+

第一种情况有8000字节。第二个有 8002 个字节，这违反了规则“最多可以有 8,000 个字节”。

"String or binary data would be truncated." 适用于 NVARCHAR 但不适用于 LIKE 操作中的 VARCHAR

"String or binary data would be truncated." for NVARCHAR but not VARCHAR in LIKE operation

sql

sql-server

nvarchar

varcharmax

sql-like