sql - 如何修改要执行的这个查询？

Question

我有以下查询，我希望它显示“尚未”，而不是显示数据库中 Status 列的 NULL 值。怎么做？

SELECT     dbo.SafetySuggestionsLog.Title, dbo.SafetySuggestionsLog.Description, dbo.SafetySuggestionsLog.Username, dbo.SafetySuggestionsStatus.Status,
                 CASE WHEN dbo.SafetySuggestionsStatus.Status  IS NULL THEN 'NOT YET'
FROM         dbo.SafetySuggestionsLog INNER JOIN
                      dbo.employee ON dbo.SafetySuggestionsLog.Username = dbo.employee.Username LEFT OUTER JOIN
                      dbo.SafetySuggestionsStatus ON dbo.SafetySuggestionsLog.StatusID = dbo.SafetySuggestionsStatus.ID
WHERE     (dbo.employee.Username = @Username)

供您参考，该数据库设计如下：

Employee Table: Username, Name
SafetySuggestionsLog Table: ID, Title, Description, Username, StatusID
SafetySuggestionsStatus: ID, Status

Answer 1

使用COALESCE或ISNULL。

SELECT     dbo.SafetySuggestionsLog.Title, dbo.SafetySuggestionsLog.Description, dbo.SafetySuggestionsLog.Username, COALESCE(dbo.SafetySuggestionsStatus.Status, "Not Yet") as 'Status'
FROM         dbo.SafetySuggestionsLog INNER JOIN
                      dbo.employee ON dbo.SafetySuggestionsLog.Username = dbo.employee.Username LEFT OUTER JOIN
                      dbo.SafetySuggestionsStatus ON dbo.SafetySuggestionsLog.StatusID = dbo.SafetySuggestionsStatus.ID
WHERE     (dbo.employee.Username = @Username)

或者

SELECT     dbo.SafetySuggestionsLog.Title, dbo.SafetySuggestionsLog.Description, dbo.SafetySuggestionsLog.Username, ISNULL(dbo.SafetySuggestionsStatus.Status, "Not Yet") as 'Status'
FROM         dbo.SafetySuggestionsLog INNER JOIN
                      dbo.employee ON dbo.SafetySuggestionsLog.Username = dbo.employee.Username LEFT OUTER JOIN
                      dbo.SafetySuggestionsStatus ON dbo.SafetySuggestionsLog.StatusID = dbo.SafetySuggestionsStatus.ID
WHERE     (dbo.employee.Username = @Username)

Answer 2

你几乎就在那里，你可以使用 ISNULL 或 CASE

CASE WHEN dbo.Blah.Status IS NULL THEN 'Not Yet' ELSE dbo.Blah.Status END

或者

isnull(dbo.Blah.Status, 'Not Yet')