SQL 如何获取表中字段使用的最大大小
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how to get the max size used by a field in table
提问by Prady
I have a field which has been set to max size. How can i find the max size occupied by the field.
我有一个已设置为最大大小的字段。我如何找到该字段占用的最大大小。
For example if the records are for table TableA
例如，如果记录是表 TableA
FieldA
123
abcd
1234567
I need to know which row occupied the most size and what the size is
我需要知道哪一行占用的大小最多，大小是多少
Thanks
谢谢
Prady
普拉迪
回答by RichardTheKiwi
LENtests for the length in characters, e.g. "a" = 1 char
LEN测试以字符为单位的长度，例如 "a" = 1 个字符
select max(len(fieldA)) from tbl
DATALENGTHchecks for the size in bytes, an NVarchar occupies 2 bytes per character
DATALENGTH检查以字节为单位的大小，一个 NVarchar 每个字符占用 2 个字节
select max(datalength(fieldA)) from tbl
To get all the rows in the table that have the maximum length of data in FieldA,
要获取表中字段A中数据长度最大的所有行，
select *
from tbl join (select MAX(LEN(fieldA)) maxlen from tbl) l
on l.maxlen = LEN(tbl.fieldA)
回答by pmac72
SELECT TOP 1 WITH TIES *
FROM tbl
ORDER BY len(tbl.fieldA) DESC
回答by ShelS
You may to query this sql
你可以查询这个sql
Select Character_Maximum_Length
From INFORMATION_SCHEMA.COLUMNS
Where TABLE_CATALOG Like 'DatabaseName' And TABLE_NAME Like 'TableName' And COLUMN_NAME Like 'FieldName'
