SQL-尝试增加值时的语法错误

Question

I'm using SQL Server in a C# project for a troubleshooting program and I have a table that contains ID,Question,QuestionId,Solution and Rank. I previously asked a question and it worked for selecting, so I tried modifying that for an Update instead. I'm trying to increment the rank of the solution with the highest rank by 1.

sql = "UPDATE dbo.Questions SET Rank = Rank + 1 q WHERE Rank=(SELECT MAX(Rank) FROM dbo.Questions i where i.QuestionId = q.QuestionId) AND q.QuestionId = " + questionId;

I get the following error with this:

Incorrect syntax near 'q' Incorrect syntax near the keyword 'AND'

Answer 1

The table alias is in the wrong place. In SQL Server, you want a FROM clause:

UPDATE q
    SET Rank = Rank + 1
    FROM dbo.Questions q
    WHERE Rank = (SELECT MAX(Rank)
                  FROM dbo.Questions i 
                  WHERE i.QuestionId = q.QuestionId
                 ) AND
         q.QuestionId = " + questionId;

You can also write this as:

UPDATE q
    SET Rank = Rank + 1
    FROM (SELECT TOP (1) q.*
          FROM dbo.Questions q
          WHERE q.QuestionId = " + questionId
          ORDER BY rank DESC
         );

This makes it obvious that you only want to update one row.

Let me also add . . . learn to use query parameters. Don't put questionId directly into the query string. That is just a way to introduce syntax errors that are really hard to debug.