想要逐行遍历表，如果另一个表中有匹配的行，则使用限制1删除

Question

我本质上是尝试手动设置减法（没有删除重复，我需要保留重复，如果它们存在）。我有一个表我想逐行迭代，如果在一个更大的表中匹配，则使用存储过程删除较大表中匹配的单个实例。我怎么能这样做？我有三个标准，并写下如下 -

DROP PROCEDURE deleteOverlappingBottles;
DELIMITER ;;

CREATE PROCEDURE deleteOverlappingBottles()
BEGIN
DECLARE n INT default 0;
DECLARE i INT default 0;
SELECT 10 FROM allBottles INTO n;
SET i = 0;
WHILE i<n DO
    #
    What goes here?  How can I get the current row of allBottles and specifically the values needed for the proceeding where clause?
    DELETE FROM historicdata2Delete as t
    WHERE t.unitADcode = ab.bottleBarcode AND t.bottle_timestamp = ab.t_stamp
    AND t.prepackId = ab.parentPrepackId LIMIT 1;
    SET i = i+1;
END WHILE;
End;
;;
DELIMITER ;

CALL deleteOverlappingBottles();

使用MySQL 5.6。

historicDataToDelete
unitADcode            bottle_timestamp        prepackId
barcode1              timestamp1              id1
barcode1              timestamp1              id1
barcode2              timestamp2              id2
barcode3              timestamp3              id3
barcode3              timestamp3              id3

allBottles
bottleBarcode         t_stamp                 parentPrepackId
barcode1              t_stamp1                id1
barcode1              t_stamp1                id1
barcode3              t_stamp3                id3

因此，逐行遍历allBottles并为每个实例删除一行将保留historicalData2Delete

historicDataToDelete
unitADcode            bottle_timestamp        prepackId
barcode2              timestamp2              id2
barcode3              timestamp3              id3

这是我迄今为止所做的，但它不起作用，任何想法为什么？

DELIMITER ;;

CREATE PROCEDURE deleteOverlappingBottles()
BEGIN
DECLARE n INT default 0;
DECLARE i INT default 0;

SELECT 10 FROM allBottles INTO n;
SET i = 0;
WHILE i<n DO
    SET @barcode = (SELECT bottleBarcode FROM allBottles LIMIT i,1);
    SET @tstamp = (SELECT t_stamp FROM allBottles LIMIT i, 1);
    SET @preIdx = (SELECT parentPrepackId FROM allBottles LIMIT i, 1);
    DELETE FROM historicdata2Delete
    WHERE unitADcode = @barcode AND bottle_timestamp = @tstamp AND prepackIdx = @preIdx LIMIT 1;
    SET i = i+1;
END WHILE;
End;
;;
DELIMITER ;

CALL deleteOverlappingBottles();

它说结果包括多行。它确实运行了一段时间，超过一个小时然后我停止它但没有删除。

Answer 1

看起来好像你只缺少一个cursor。

参考代码可以在这里找到：MySql Cursors

CREATE PROCEDURE deleteOverlappingBottles()
BEGIN
DECLARE done INT DEFAULT FALSE;
-- Variables for FETCH (change data types to your needs)
DECLARE vBottleBarcode CHAR(100);
DECLARE vt_stamp TIMESTAMP;
DECLARE vParentPrepackId INT;
-- cursor to iterate through the table
DECLARE cur1 CURSOR FOR SELECT BottleBarcode, t_stamp, ParentPrepackId FROM allBottles;
-- apparently MySql needs this to handle the end of the table
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

OPEN cur1;

read_loop: LOOP
    -- get the three column values for the current row
    FETCH cur1 INTO vBottleBarcode, vt_stamp, vParentPrepackId;
    IF done THEN
      LEAVE read_loop;
    END IF;
    -- use the variables from FETCH to identify the row in historicdataToDelete
    DELETE FROM historicdata2Delete as t
    WHERE t.unitADcode = vBottleBarcode AND t.bottle_timestamp = vt_stamp
    AND t.prepackId = vParentPrepackId
    LIMIT 1; -- delete only 1 row
  END LOOP;

  CLOSE cur1;
END LOOP;
End;

免责声明：我不熟悉MySql。语法可能略有错误，请适应您的需求。