SQL Server 顯式游標完整語法：宣告、開啟、迴圈、關閉與釋放

標準流程

-- 1. 宣告游標
DECLARE MyCursor CURSOR FOR 
    SELECT TOP 5 FBookName, FBookCoding FROM TBookInfo;

-- 2. 開啟游標
OPEN MyCursor;

-- 3. 宣告接收變數
DECLARE @BookName NVARCHAR(2000), @BookCoding NVARCHAR(2000);

-- 4. 取第一筆
FETCH NEXT FROM MyCursor INTO @BookName, @BookCoding;

-- 5. 迴圈處理
WHILE @@FETCH_STATUS = 0
BEGIN
    PRINT 'name: ' + @BookName;
    FETCH NEXT FROM MyCursor INTO @BookName, @BookCoding;
END

-- 6. 關閉與釋放
CLOSE MyCursor;
DEALLOCATE MyCursor;

完整範例（含暫存表測試）

CREATE TABLE #a (id VARCHAR(20), name VARCHAR(20));
INSERT INTO #a VALUES ('1','jack'), ('2','join'), ('3','make');

DECLARE mycursor CURSOR FOR SELECT * FROM #a;
OPEN mycursor;
DECLARE @id VARCHAR(20), @name VARCHAR(20);
FETCH NEXT FROM mycursor INTO @id, @name;
WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @id, @name;
    FETCH NEXT FROM mycursor INTO @id, @name;
END
CLOSE mycursor;
DEALLOCATE mycursor;

效能警示

游標屬逐列操作（RBAR），資源消耗極大。SQL 引擎優化對象是集合，能用集合操作（JOIN/WHERE/窗口函數）絕不使用游標。大量資料下游標是效能殺手。