想要逐行遍历 table，如果在另一个 table 中有匹配的行，则删除限制为 1

Question

我基本上是在尝试手动进行集合减法（不删除重复项，如果存在重复项，我需要保留它们）。我有一个 table 我想逐行迭代，如果在更大的 table 中有匹配项，请使用更大的 table 删除匹配项的单个实例存储过程。我该怎么做？我有三个 where 标准并写了以下内容 -

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 historicData2Delete

historicDataToDelete
unitADcode            bottle_timestamp        prepackId
barcode2              timestamp2              id2
barcode3              timestamp3              id3

这是我目前所拥有的，但它不起作用，关于原因的任何想法？

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();

它说结果不止一行。之前运行有一段时间，一个多小时后我停止了它，但没有删除任何内容。

Answer 1

看来你只是少了一个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，请根据您的需要进行调整。

想要逐行遍历 table，如果在另一个 table 中有匹配的行，则删除限制为 1

Want to iterate over a table row by row, and if there's a matching row in another table, delete with limit 1

sql

mysql-5.6