SQL 区分大小写比较

Question

我想用 CASE 语句知道两个字段是否相同。

我通过以下查询设法做到了，但我想知道是否有更好的方法？我只想让“=”进行区分大小写的比较。我尝试使用 COLLATE 但随后我需要使用 WHERE 子句来过滤我的结果，我想要所有行。使用 HASHBYTES 似乎有些过分，尤其是当我需要将它与 ISNULL

结合使用时

DECLARE @myTable AS TABLE (old varchar(255), new varchar(255));
INSERT INTO @myTable VALUES
    ('test', 'test'),
    ('test', 'TEST'),
    (null, null)


SELECT old, new, 
    CASE WHEN HASHBYTES('SHA2_512', old) = HASHBYTES('SHA2_512', new) THEN 'same' ELSE 'changed' END AS updated,
    CASE WHEN HASHBYTES('SHA2_512', ISNULL(old, '')) = HASHBYTES('SHA2_512', ISNULL(new, '')) THEN 'same' ELSE 'changed' END AS updated_isnull
FROM @myTable
--where old = new COLLATE Latin1_General_CS_AS

我需要专栏'updated_isnull'

| old  | new  | updated | updated_isnull |
| ---- | ---- | ------- | -------------- |
| test | test | same    | same           |
| test | TEST | changed | changed        |
| NULL | NULL | changed | same           |

Answer 1

正确的解决方案是修复您的列，以便您的数据存储在区分大小写的排序规则中。那么你只需要做：

select old, new,
    case when old = new
             or (old is null and new is null)
         then 1
        else 0 
    end as is_same
from @mytable

使用不区分大小写的排序规则，我们可以像这样解决

select old, new,
    case when old collate Latin1_General_Bin = new collate Latin1_General_Bin 
             or (old is null and new is null)
         then 1
        else 0 
    end as is_same
from @mytable

Demo on DB Fiddle:

old  | new  | is_same
:--- | :--- | ------:
test | test |       1
test | TEST |       0
null | null |       1

Answer 2

试试这个：

DECLARE @myTable AS TABLE (old varchar(255), new varchar(255));
INSERT INTO @myTable VALUES
    ('test', 'test'),
    ('test', 'TEST'),
    (null, null)


SELECT old, new,
    CASE WHEN old COLLATE Latin1_General_CS_AS = new COLLATE Latin1_General_CS_AS THEN 'same' ELSE 'changed' END AS updated,
    CASE WHEN isnull(old,0) COLLATE Latin1_General_CS_AS = isnull(new,0) COLLATE Latin1_General_CS_AS THEN 'same' ELSE 'changed' END AS updated_isnull
FROM @myTable

SQL 区分大小写比较

SQL case sensitive compare

sql

sql-server

string

case

sql-null