Question

我使用下面的SQL更新语句将所有空值替换为“不需要签名”，但是当我运行它时，我的空白量与我开始时相同。我做错了什么？

BEGIN TRANSACTION; 
UPDATE 
    shipments
SET 
    signature_required = REPLACE(signature_required,'','Signature not required')
WHERE 
    signature_required = ''
Commit Transaction;

Answer 1

删除＆＃39;替换＆＃39>简化set语句。功能。使用WHERE子句定位空白值。

UPDATE 
shipments
SET 
signature_required = 'Signature not required'
WHERE 
signature_required = ''

仅当值实际存储为空字符串时才会起作用。

Answer 2

你必须放一个空格

BEGIN TRANSACTION; 
UPDATE 
    shipments
SET 
    signature_required = REPLACE(signature_required,' ','Signature not required')
WHERE 
    signature_required = ' '
Commit Transaction;

或

BEGIN TRANSACTION; 
UPDATE 
    shipments
SET 
    signature_required = REPLACE(isnull(Signature_required,' '),' ','Signature not required')
WHERE 
    ISNULL(signature_required,' ') = ' '
Commit Transaction;

Answer 3

如果'blank'表示空字符串或null，则使用coalesce()返回空字符串进行比较将起作用：

update shipments
set signature_required = 'signature not required'
where coalesce(signature_required,'') = '';

或使用or

update shipments
set signature_required = 'signature not required'
where signature_required = ''
   or signature_required is null

使用Update语句替换空格

3 个答案: