MySQL: Update a “sort” column accoreding to ORDER BY

问题

Fully edited: My query has 2 columns from 2 tables: filename and sortorder.

Full tables are done here http://sqlfiddle.com/#!9/8c0507

Example:

SELECT * FROM table1 t1
  LEFT JOIN table2 t2
    ON t1.idmd5 = t2.imgid
ORDER BY t2.filename
WHERE t1.anotherid = "123456";

Output:

filename-01.jpg   - 12
filename-02.jpg   - 73
filename-03.jpg   - 1
filename-12.jpg   - 63
filename-24.jpg   - 99

Now, the "sortorder" column should be re-set according to the ORDER BY - output, it should start at 1.

Expected result:

filename-01.jpg   - 1
filename-02.jpg   - 2
filename-03.jpg   - 3
filename-12.jpg   - 4
filename-24.jpg   - 5

How to achieve that?

回答1:

Here's the query:

Assigning a row number to each file name after sorting in ASCENDING ORDER.
Later making an INNER JOIN between the table alias t and your table YT on matching filename and setting the t.rn (row number/new sort order) to the YT.sortOrder column.

UPDATE 
your_table YT 
INNER JOIN 
(
    SELECT 
        fileName,
        @rowNumber := @rowNumber + 1 AS rn
    FROM your_table , (SELECT @rowNumber := 0) var
    ORDER BY fileName ASC
) AS t
ON YT.fileName = t.fileName
SET YT.sortOrder = t.rn;

Demo Before update

Facing problems to access SQL FIDDLE

TEST SCHEMA(with data):

DROP TABLE IF EXISTS `your_table`;
CREATE TABLE `your_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `filename` varchar(50) NOT NULL,
  `sortOrder` int(11) NOT NULL,
  PRIMARY KEY (`id`)
);
INSERT INTO `your_table` VALUES ('1', 'f1', '12');
INSERT INTO `your_table` VALUES ('2', 'f2', '73');
INSERT INTO `your_table` VALUES ('3', 'f3', '1');
INSERT INTO `your_table` VALUES ('4', 'f4', '63');
INSERT INTO `your_table` VALUES ('5', 'f5', '99');

SELECT 
*
FROM your_table;

id  filename   sortOrder
1      f1         12
2      f2         73
3      f3          1
4      f4         63
5      f5         99

**Now Run the above query**



SELECT 
*
FROM your_table;

FINAL OUTPUT:

id  filename   sortOrder
1      f1         1
2      f2         2
3      f3         3
4      f4         4
5      f5         5

EDIT: (Based on the changes in the requirement)

UPDATE 
tableone TOne 
INNER JOIN 
(
  SELECT
        t1.file_id,
        t2.IMG_FILENAME,
        @rowNumber := @rowNumber + 1 AS rn
    FROM
    tableone t1
    LEFT JOIN tabletwo t2 ON t1.FILE_ID = t2.IMG_ID
    CROSS JOIN (SELECT @rowNumber := 0) AS var
    ORDER BY t2.IMG_FILENAME ASC
) AS t
ON TOne.file_id = t.file_id
SET TOne.Order = t.rn;

Test Data And Schema:

DROP TABLE IF EXISTS `tableone`;
CREATE TABLE `tableone` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `order` int(11) NOT NULL,
  `file_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
);
INSERT INTO `tableone` VALUES ('1', '12', '1');
INSERT INTO `tableone` VALUES ('2', '73', '2');
INSERT INTO `tableone` VALUES ('3', '1', '3');
INSERT INTO `tableone` VALUES ('4', '63', '4');
INSERT INTO `tableone` VALUES ('5', '99', '5');


DROP TABLE IF EXISTS `tabletwo`;
CREATE TABLE `tabletwo` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `img_id` int(11) NOT NULL,
  `img_filename` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
);

INSERT INTO `tabletwo` VALUES ('1', '1', 'filename-01.jpg ');
INSERT INTO `tabletwo` VALUES ('2', '2', 'filename-02.jpg ');
INSERT INTO `tabletwo` VALUES ('3', '3', 'filename-03.jpg ');
INSERT INTO `tabletwo` VALUES ('4', '4', 'filename-04.jpg ');
INSERT INTO `tabletwo` VALUES ('5', '5', 'filename-05.jpg ');

Run the above (UPDATE) query operation and see the result

BEFORE UPDATING: SQL FIDDLE DEMO

AFTER UPDATING: SQL FIDDLE DEMO

来源：https://stackoverflow.com/questions/38357583/mysql-update-a-sort-column-accoreding-to-order-by

标签

mysql

select

columnsorting