Mysql 如果列总和小于X，则更新行

我试图找出如果表中的行的总大小小于

x

，如何更新这些行

以下是我的设置：

create table test_limit (
       id int not null auto_increment primary key,
       folder varchar(255),
       status varchar(32) DEFAULT 'awaiting',
       size bigint unsigned default 0,
       request_id varchar(32)
)
ENGINE=InnoDB;

insert into test_limit
  (folder, status, size)
values
  ('/tmp/AAA/bar', 'awaiting', 200 ),
  ('/tmp/AAA/bar', 'awaiting', 200 ),
  ('/tmp/AAA/bar', 'awaiting', 200 ),
  ('/tmp/BBB/bar', 'awaiting', 200 ),
  ('/tmp/BBB/bar', 'awaiting', 200 );

我有一个包含5行的表，每行都有一个大小。我要做的是更新一组行：

• 具有相同的

  文件夹

  值
• 状态不在

  进行中

  或

  已创建

• 总限额为400

我想出了以下更新命令：

SET @request_id='bbb';
UPDATE test_limit t1
  JOIN
     ( SELECT folder FROM test_limit WHERE status = 'awaiting' GROUP BY folder limit 1) t2
    ON t1.folder = t2.folder
  LEFT JOIN
     ( SELECT folder FROM test_limit WHERE status IN ('in_progress', 'created') GROUP BY folder limit 1) t3
    ON t1.folder = t3.folder
  JOIN
     ( SELECT id, @total := @total + size AS total  FROM (test_limit, (select @total := 0) t)  WHERE @total < 400 and status='awaiting') t4
    ON t1.id=t4.id
  SET t1.status = 'in_progress',
      t1.request_id = @request_id
  WHERE t1.status = 'awaiting' AND t3.folder is NULL;

更新：

上述结果对于第一次运行是正确的。我想在第二次运行中实现什么（比如请求_id='aaa'）：

在第三次运行中，它不应该更新任何内容，因为所有的值都“正在进行”

---

如何实现这一点？

下面是一个使用存储过程的解决方案。尽管它比使用查询的解决方案要长，但您可能会发现此过程代码更易于理解和维护。当然，执行起来很方便：

CALL process_test_limit('AAA');

它是如何工作的？该过程从

test\u limit

文件夹中获取按

文件夹排序的行，并跟踪
id
，直到运行总数达到400或
文件夹发生更改。如果文件夹中已有状态为“正在处理”的记录，则该文件夹将被忽略

DROP PROCEDURE IF EXISTS `process_test_limit`;
DELIMITER $$
CREATE PROCEDURE `process_test_limit` (IN p_request_id VARCHAR(32))
BEGIN

    DECLARE v_sqlsafeupdates  BOOLEAN;  -- State of SQL_SAFE_UPDATES at execution start
    DECLARE v_to_update       CHAR(64); -- Name of temp table to store IDs of rows to be updated
    DECLARE v_id              INT;
    DECLARE v_folder          VARCHAR(255);
    DECLARE v_size            BIGINT UNSIGNED;
    DECLARE v_running_total   BIGINT UNSIGNED  DEFAULT 0;
    DECLARE v_prev_id         INT              DEFAULT NULL;
    DECLARE v_prev_folder     VARCHAR(255)     DEFAULT NULL;

    -- Cursor end handler flag (must be declared before cursors)
    DECLARE v_cursor_end   BOOLEAN DEFAULT FALSE;

    -- Main cursor to iterate through the rows of test_limit
    DECLARE c_test_limit CURSOR FOR
    SELECT tl.id
         , tl.folder
         , tl.size
      FROM test_limit tl
     WHERE tl.status = 'awaiting'
       AND NOT EXISTS (SELECT 1 
                         FROM test_limit tl_check
                        WHERE tl_check.folder = tl.folder
                          AND tl_check.status = 'in_progress'
                        LIMIT 1
                      )
     ORDER BY tl.folder -- Order is important: we process max one folder per call
            , tl.size
    ;

    -- Cursor end handler
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_cursor_end = TRUE;

    -- Remember the current state of SQL_SAFE_UPDATES, then disable it
    SET v_sqlsafeupdates = @@sql_safe_updates;
    SET @@sql_safe_updates = FALSE;

    -- Create temp table for tracking IDs of rows to update
    SET v_to_update = CONCAT(
        'process_test_limit_', CAST(UNIX_TIMESTAMP() AS CHAR), '_tmp'
    );
    SET @create_tmp_table_sql = CONCAT(
        'CREATE TEMPORARY TABLE ', v_to_update, 
        ' (id INT NOT NULL PRIMARY KEY) ENGINE=MEMORY'
    );
    PREPARE create_tmp_table_stmt FROM @create_tmp_table_sql;
    EXECUTE create_tmp_table_stmt;
    DEALLOCATE PREPARE create_tmp_table_stmt;

    -- Prepare statement for saving IDs into "to update" tmp table
    SET @save_id_sql = CONCAT('INSERT INTO ', v_to_update, ' (id) VALUES (?)');
    PREPARE save_id_stmt FROM @save_id_sql;

    -- Open the cursor to enable us to read the ordered result set one record at a time
    OPEN c_test_limit;

    -- Process the ordered test_limit records one-by-one
    l_test_limit: LOOP

        -- Get the next record (advance the cursor)
        FETCH c_test_limit
         INTO v_id, v_folder, v_size
        ;

        -- Exit the loop if there are no more records to process
        IF v_cursor_end THEN
            LEAVE l_test_limit;
        END IF;

        -- First/same-as-last folder and running total not over 400? Save ID for update.
        IF (v_prev_folder IS NULL OR v_folder = v_prev_folder) AND v_running_total + v_size <= 400 THEN

            SET @id = CAST(v_id AS CHAR);
            EXECUTE save_id_stmt USING @id;

            -- Set variables for next iteration
            SET v_prev_id = v_id;
            SET v_prev_folder = v_folder;
            SET v_running_total = v_running_total + v_size;

        -- Different folder or running total over 400? Exit loop.
        ELSE

            LEAVE l_test_limit;

        END IF;

    END LOOP;

    -- Deallocate statement for inserting rows into temp table
    DEALLOCATE PREPARE save_id_stmt;

    -- Update rows
    SET @update_sql = CONCAT(
        'UPDATE test_limit t INNER JOIN ', v_to_update, ' tmp',
            ' ON t.id = tmp.id',
            ' SET t.status = ?,',
            ' t.request_id = ?'
    );
    SET @status = 'in_progress';
    SET @request_id = p_request_id;
    PREPARE update_stmt FROM @update_sql;
    EXECUTE update_stmt USING @status, @request_id;
    DEALLOCATE PREPARE update_stmt;

    -- Drop temp table
    SET @drop_tmp_table_sql = CONCAT('DROP TEMPORARY TABLE ', v_to_update);
    PREPARE drop_tmp_table_stmt FROM @drop_tmp_table_sql;
    EXECUTE drop_tmp_table_stmt;
    DEALLOCATE PREPARE drop_tmp_table_stmt;

    -- Return SQL_SAFE_UPDATES to its original state at execution start
    SET @@sql_safe_updates = v_sqlsafeupdates;

END$$
DELIMITER ;

我花了一些时间来思考逻辑。下面是sql小提琴

我同意扎克的方向，但要想弄清楚你到底想要什么有点困难。你给了我们你不想要的结果，但不是你想要的结果。@Matt yes，You right=），我已经更新了我的答案，包括了我希望在下一次sql执行中实现的目标。啊，我明白了，所以400是上限，你想根据运行总数进行更新。。。。。。我不得不想一想，我在mysql中并没有做太多，sql server、oracle等中的快速窗口功能可以让您快速到达目的地……但它们都大于400@草莓，抱歉如果我不够清楚，我想马特总结了我想要实现的目标。非常感谢你的回答。这个查询所做的一件事是——它将所有记录更新为“进行中”哦，好的。因此，我需要做的第一件事是将>=400更改为=400。让我也参考一下你的更新。在阅读了你的更新之后，我同意我的查询并不能解决你的问题。如果（比如）大小值是模式化的和可预测的，我可能能够在
UPDATE
语句中设想一个解决方案。但我认为最好是编写一个存储过程。算法将更容易理解，性能也会更好。您是否愿意将存储过程作为一种解决方案？是的，存储过程绝对是可选的。如果你能在这方面帮助我，我将不胜感激。你好！请查看上面的存储过程，并让我知道它是否对您有帮助。@vor因此，如果这对您有效，我很好奇？需要调整吗？
CALL process_test_limit('AAA');

DROP PROCEDURE IF EXISTS `process_test_limit`;
DELIMITER $$
CREATE PROCEDURE `process_test_limit` (IN p_request_id VARCHAR(32))
BEGIN

    DECLARE v_sqlsafeupdates  BOOLEAN;  -- State of SQL_SAFE_UPDATES at execution start
    DECLARE v_to_update       CHAR(64); -- Name of temp table to store IDs of rows to be updated
    DECLARE v_id              INT;
    DECLARE v_folder          VARCHAR(255);
    DECLARE v_size            BIGINT UNSIGNED;
    DECLARE v_running_total   BIGINT UNSIGNED  DEFAULT 0;
    DECLARE v_prev_id         INT              DEFAULT NULL;
    DECLARE v_prev_folder     VARCHAR(255)     DEFAULT NULL;

    -- Cursor end handler flag (must be declared before cursors)
    DECLARE v_cursor_end   BOOLEAN DEFAULT FALSE;

    -- Main cursor to iterate through the rows of test_limit
    DECLARE c_test_limit CURSOR FOR
    SELECT tl.id
         , tl.folder
         , tl.size
      FROM test_limit tl
     WHERE tl.status = 'awaiting'
       AND NOT EXISTS (SELECT 1 
                         FROM test_limit tl_check
                        WHERE tl_check.folder = tl.folder
                          AND tl_check.status = 'in_progress'
                        LIMIT 1
                      )
     ORDER BY tl.folder -- Order is important: we process max one folder per call
            , tl.size
    ;

    -- Cursor end handler
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_cursor_end = TRUE;

    -- Remember the current state of SQL_SAFE_UPDATES, then disable it
    SET v_sqlsafeupdates = @@sql_safe_updates;
    SET @@sql_safe_updates = FALSE;

    -- Create temp table for tracking IDs of rows to update
    SET v_to_update = CONCAT(
        'process_test_limit_', CAST(UNIX_TIMESTAMP() AS CHAR), '_tmp'
    );
    SET @create_tmp_table_sql = CONCAT(
        'CREATE TEMPORARY TABLE ', v_to_update, 
        ' (id INT NOT NULL PRIMARY KEY) ENGINE=MEMORY'
    );
    PREPARE create_tmp_table_stmt FROM @create_tmp_table_sql;
    EXECUTE create_tmp_table_stmt;
    DEALLOCATE PREPARE create_tmp_table_stmt;

    -- Prepare statement for saving IDs into "to update" tmp table
    SET @save_id_sql = CONCAT('INSERT INTO ', v_to_update, ' (id) VALUES (?)');
    PREPARE save_id_stmt FROM @save_id_sql;

    -- Open the cursor to enable us to read the ordered result set one record at a time
    OPEN c_test_limit;

    -- Process the ordered test_limit records one-by-one
    l_test_limit: LOOP

        -- Get the next record (advance the cursor)
        FETCH c_test_limit
         INTO v_id, v_folder, v_size
        ;

        -- Exit the loop if there are no more records to process
        IF v_cursor_end THEN
            LEAVE l_test_limit;
        END IF;

        -- First/same-as-last folder and running total not over 400? Save ID for update.
        IF (v_prev_folder IS NULL OR v_folder = v_prev_folder) AND v_running_total + v_size <= 400 THEN

            SET @id = CAST(v_id AS CHAR);
            EXECUTE save_id_stmt USING @id;

            -- Set variables for next iteration
            SET v_prev_id = v_id;
            SET v_prev_folder = v_folder;
            SET v_running_total = v_running_total + v_size;

        -- Different folder or running total over 400? Exit loop.
        ELSE

            LEAVE l_test_limit;

        END IF;

    END LOOP;

    -- Deallocate statement for inserting rows into temp table
    DEALLOCATE PREPARE save_id_stmt;

    -- Update rows
    SET @update_sql = CONCAT(
        'UPDATE test_limit t INNER JOIN ', v_to_update, ' tmp',
            ' ON t.id = tmp.id',
            ' SET t.status = ?,',
            ' t.request_id = ?'
    );
    SET @status = 'in_progress';
    SET @request_id = p_request_id;
    PREPARE update_stmt FROM @update_sql;
    EXECUTE update_stmt USING @status, @request_id;
    DEALLOCATE PREPARE update_stmt;

    -- Drop temp table
    SET @drop_tmp_table_sql = CONCAT('DROP TEMPORARY TABLE ', v_to_update);
    PREPARE drop_tmp_table_stmt FROM @drop_tmp_table_sql;
    EXECUTE drop_tmp_table_stmt;
    DEALLOCATE PREPARE drop_tmp_table_stmt;

    -- Return SQL_SAFE_UPDATES to its original state at execution start
    SET @@sql_safe_updates = v_sqlsafeupdates;

END$$
DELIMITER ;

-- Execution 1: 'AAA'
CALL process_test_limit('AAA');
SELECT * FROM test_limit;
-- id, folder, status, size, request_id
-- 1, /tmp/AAA/bar, in_progress, 200, AAA
-- 2, /tmp/AAA/bar, in_progress, 200, AAA
-- 3, /tmp/AAA/bar, awaiting, 200, 
-- 4, /tmp/BBB/bar, awaiting, 200, 
-- 5, /tmp/BBB/bar, awaiting, 200, 

-- Execution 2: 'BBB'
CALL process_test_limit('BBB');
SELECT * FROM test_limit;
-- id, folder, status, size, request_id
-- 1, /tmp/AAA/bar, in_progress, 200, AAA
-- 2, /tmp/AAA/bar, in_progress, 200, AAA
-- 3, /tmp/AAA/bar, in_progress, 200,
-- 4, /tmp/BBB/bar, awaiting, 200, BBB
-- 5, /tmp/BBB/bar, awaiting, 200, BBB

-- Execution 3: 'CCC'
CALL process_test_limit('CCC');
SELECT * FROM test_limit;
-- id, folder, status, size, request_id
-- 1, /tmp/AAA/bar, in_progress, 200, AAA
-- 2, /tmp/AAA/bar, in_progress, 200, AAA
-- 3, /tmp/AAA/bar, in_progress, 200,
-- 4, /tmp/BBB/bar, in_progress, 200, BBB
-- 5, /tmp/BBB/bar, in_progress, 200, BBB

UPDATE test_limit u
JOIN
(
  SELECT
    t1.*
    ,f.NonAwaitingFolderTotal
    ,(@runtot := @runtot + t1.size) as RunningTotal
  FROM
    (
      SELECT
        folder
        ,SUM(CASE WHEN status <> 'awaiting' THEN size ELSE 0 END) as NonAwaitingFolderTotal
      FROM
        test_limit t
      GROUP BY
        folder
      HAVING
        SUM(CASE WHEN status <> 'awaiting' THEN size ELSE 0 END) <= 400
      ORDER BY
        NonAwaitingFolderTotal, folder
      LIMIT 1
    ) f
    INNER JOIN test_limit t1
    ON f.folder = t1.folder
    CROSS JOIN (SELECT @runtot:=0) var
  WHERE
    t1.status = 'awaiting'
)  t2
ON u.id = t2.id
AND (t2.NonAwaitingFolderTotal + t2.RunningTotal) <= 400
SET
  u.status = 'in_progress'
  ,u.request_id = @request_id
;

SELECT 
  *
  ,(@foldercount := IF(@prevfolder=folder,@foldercount,@foldercount+1)) as FolderNum
  ,(@rownum := @rownum + 1) as RowNum
  ,(@grouprownum := IF(@prevfolder=folder,@grouprownum+1,1)) as GroupRowNum
  ,(@total := IF(@prevfolder=folder,@total + t.size,t.size)) as GroupRunningTotal
  ,(@GroupAwaitRunningTotal := IF(
        @prevfolder=folder
        ,IF(t.status = 'awaiting',@GroupAwaitRunningTotal + t.size,@GroupAwaitRunningTotal)
        ,IF(t.status = 'awaiting',t.size,0)
      )
   ) as GroupAwaitRunningTotal
   ,(@GroupNonAwaitRunningTotal := IF(
        @prevfolder=folder
        ,IF(t.status != 'awaiting',@GroupNonAwaitRunningTotal + t.size,@GroupNonAwaitRunningTotal)
        ,IF(t.status != 'awaiting',t.size,0)
      )
   ) as GroupNonAwaitRunningTotal
  ,(@runtot := @runtot + t.size) as RunningTotal
  ,@prevfolder:=folder
FROM 
  test_limit t
  CROSS JOIN
  (SELECT @prevfolder:=NULL, @GroupAwaitRunningTotal := 0
     ,@GroupNonAwaitRunningTotal := 0
     ,@total:=0, @rownum:=0, @grouprownum:=0, @runtot:=0, @foldercount:=0) var