mysql update a table with LOAD DATA - mysql

Question

So I have someone working on a csv (generated from my table) where they will be updating some fields by hand. This may happen multiple times. I'd like to take the modified csv and update my existing table.
From my understanding, I will need to create a tmp table and then use that to update the existing table. So I can create the temporary table, but how can I iterate through that table and use it to update the existing table?
My sql querying skills are pretty basic. I think its possible, but I'm not sure where to start.

Answer 1

You don't need a temporary table. Just make sure the CSV file includes the primary key of the table. Then you can use the REPLACE modifier in LOAD DATA INFILE. From the documentation:
If you specify REPLACE, input rows replace existing rows. In other words, rows that have the same value for a primary key or unique index as an existing row.

Answer 2

In the CSV you are generating that gets edited, you must include a unique value that will allow you to match the edited record to the original record. Make sure the user doesn't change that column! Also, make sure you have a unique key on that column.
You can then import the edited data into a table with the same (or at least very similar) structure as the original table.
Once the data is imported, you can use an INSERT ... ON DUPLICATE KEY UPDATE ... statement to update the original table. Here's an example:
Main data table:
DROP TABLE IF EXISTS `my_table`;
CREATE TABLE IF NOT EXISTS `my_table` (
`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT 'Primary Key',
`fld1` VARCHAR(100) NULL,
`fld2` VARCHAR(100) NULL,
`fld3` VARCHAR(100) NULL,
PRIMARY KEY (`id`)
)
ENGINE=MyISAM
AUTO_INCREMENT=1
DEFAULT CHARSET=utf8
COLLATE=utf8_unicode_ci;
Temporary table for edited CSV import:
DROP TABLE IF EXISTS `import_table`;
CREATE TABLE IF NOT EXISTS `import_table` (
`n_id` INT(10) NOT NULL COMMENT 'Original Primary Key',
`n_fld1` VARCHAR(100) NULL,
`n_fld2` VARCHAR(100) NULL,
`n_fld3` VARCHAR(100) NULL,
PRIMARY KEY (`id`)
)
ENGINE=MyISAM
AUTO_INCREMENT=1
DEFAULT CHARSET=utf8
COLLATE=utf8_unicode_ci;
Simulated data before export and editing:
INSERT INTO `my_table`
(`fld1`,`fld2`,`fld3`)
VALUES
('John','Doe','Atlanta'),
('Jane','Smith','New York'),
('Bill','Howe','San Antonio'),
('Harry','Fields','Paris');
Simulate the imported, edited records:
INSERT INTO `import_table`
(`n_id`,`n_fld1`,`n_fld2`,`n_fld3`)
VALUES
(1,'John','Doe','Decatur, IL'),
(2,'Jane','Smithsonian','New York, NY'),
(3,'Bill','Bellweather','San Antonio, TX'),
(4,'Harry','Belefonte','Houston, TX');
Merge the imported, edited records bak into the main table:
INSERT INTO `my_table`
(`id`,`fld1`,`fld2`,`fld3`)
SELECT `n_id`,`n_fld1`,`n_fld2`,`n_fld3`
FROM `import_table`
ON DULPICATE KEY UPDATE
`fld1` = `n_fld1`,
`fld2` = `n_fld2`,
`fld3` = `n_fld3`;