Question

在我的表supportContacts中，我有一个名为comments的字段。我试图运行一个SQL查询，当字段不为空或为null时更新/附加新注释。此注释主要来自表单内的文本框区域，当用户提交为空时，查询不应更新数据库中的字段。下面的查询给了我一个错误。 SQLFIDDLE

UPDATE supportContacts SET IF(comments = CONCAT(comments, "Append this comment") IS NOT NULL or comments = '', 'empty', comments) WHERE id=1;

Answer 1

将条件放在where子句中：

UPDATE supportContacts
    SET Comments = CONCAT(comments, 'Append this comment')
    WHERE id = 1 and Comments is not null and Comments <> '';

编辑：

您可以测试附加值是NULL还是空：

UPDATE supportContacts
    SET Comments = CONCAT(comments, @AppendComments)
    WHERE id = 1 and Comments is not null and Comments <> '' and
          @AppendComments is not null and AppendComments <> '';

但我认为这就是你想要的：

UPDATE supportContacts
    SET Comments = CONCAT(coalesce(comments, ''), @AppendComments)
    WHERE id = 1 and @AppendComments is not null ;

如果新评论为空，则无效。即使现有注释为空，它也会附加新注释。

仅当新值不为空或为null时才更新文本字段

1 个答案: