如何更新許多行並從選擇子查詢並獲取MySQL中的位置值

Question

我想從select中更新10000行，當我具有where條件的值來自相同的select子查詢時。例如。

UPDATE TableA A 
SET col1 = @val1, col2 = @val2 
WHERE col3 = @val3; 
All @val value I get from SELECT statement. 
SELECT @val1, @val2, @val3 From TableB B 
WHERE B.Key = (condition). 

Answer 1

試試這個：

UPDATE TableA A 
JOIN TableB B 
ON B.val3 = A.col3 
SET A.col1 = b.val1, 
    A.col2 = b.val2 
WHERE B.Key = (condition) 

Answer 2

幫我解決我的問題。 我很難確定這是否是最簡單的解決方案，但適用於我。

CREATE PROCEDURE cursor_ROWPERROW() 
BEGIN 
    DECLARE val1 INT; 
    DECLARE val2 VARCHAR(30); 
    DECLARE val3 VARCHAR(30); 
    DECLARE done INT DEFAULT FALSE; 
    DECLARE cursor_i CURSOR FOR SELECT val1,val2, val3 FROM table_A 
WHERE = (condition); 
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; 
    OPEN cursor_i; 
read_loop: LOOP 
    FETCH cursor_i INTO val1,val2, val3; 
    IF done THEN 
     LEAVE read_loop; 
    END IF; 
    UPDATE TableA A 
    SET A.valA1 = val1, A.valA2 = val2 
    WHERE A.valA3 = val3; 
    END LOOP; 
    CLOSE cursor_i; 
END; 
;;