如何在Sybase更新語句中使用變量

Question

此查詢用於證明一個概念，我最終將使用該概念來定位具有特定值的所有列，然後創建名稱/值對以導出到JSON。但我卡住了。

我查詢了sql表中所有列的列表。然後，我想逐行瀏覽Table1中的列，並使用變量更新值來構造查詢。例如，它通過讀取列表，如果COL4 =「古文字」，那麼我想設置上校4 =「新文本」

DECLARE @c varCHAR(100) 
DECLARE ReadData CURSOR 
FOR SELECT cname FROM sys.syscolumns WHERE creator = 'dbserver' AND tname = 'Table1' 
    DECLARE @RowCount INT 

SET @RowCount = (SELECT COUNT(cname) FROM sys.syscolumns WHERE creator = 'dbserver' AND tname = 'Table1') 
OPEN ReadData 

DECLARE @I INT // iterator 

SET @I = 1 // initialize 
WHILE (@I <= @RowCount) 
BEGIN 
FETCH NEXT ReadData INTO @c 

INSERT INTO serverdb.Table2 (cname)VALUES(@c)// this works inserting all 100 columns in the cname column of Table 2 

UPDATE serverdb.Table1 SET @c = 'New text' WHERE @c = 'Old text'// this fails with a syntax error. @c is not being interpreted for the query. Note: If I hard code the @c var (for testing)to a known column name, the query works as well 

SET @I = @I + 1 
END; 

爲什麼不更新語句識別變量的值？我錯過了什麼？

Answer 1

當你使用下面提到的varibale時，它被認爲是一個字符串。

UPDATE serverdb.Table1 SET @c = 'New text' WHERE @c = 'Old text' 

您需要創建一個動態查詢。使用execute方法來執行動態查詢

declare @sql varchar(999) 
SELECT @sql = 'UPDATE serverdb.Table1 SET '+ @c + '= ''New text'' WHERE '+ @c+ ' = ''Old text'' ' 
execute(@sql) 

希望這有助於