Sum duplicate's values when using LOAD FILE

Question

I have a table:

| foo | bar |
+-----+-----+
| abc |   4 |
| def |   1 |
| ghi |   2 |

foo has unique index.
I want to load a file into this table summing bar values of duplicates by foo column:

abc \t 7
ghi \t 3
jkl \t 4

Is there any way to sum values in duplicate rows during LOAD DATA?
This command replaces old values in a row:

LOAD DATA LOCAL INFILE 'file.txt' REPLACE
INTO TABLE `table` FIELDS TERMINATED BY '\t' (`foo`,`bar`);

I want to have a table like this:

| foo | bar |
+-----+-----+
| abc |  11 |
| def |   1 |
| ghi |   5 |
| jkl |   4 |

Answer 1

There is no direct way to achieve what you want since the source of the records are from a file and not from a table. Follow this steps to insert new row or update existing row.

• create a temporary table which serves as a temporary target table for the records.
• load the records into the temporary table assuming the new table is named TempTable and has two columns: foo, and bar

table creation ddl:

CREATE TABLE TempTable
(
    foo VARCHAR(30),
    bar INT
);

LOAD DATA LOCAL INFILE 'file.txt' 
REPLACE INTO TABLE TempTable 
FIELDS TERMINATED BY '\t' (`foo`,`bar`);

• after the records has been loaded, let's start with the combining of records. MySQL has implemented a feature called INSERT...ON DUPLICATE UPDATE, which basically inserts a new records but if the record conflicts with the existing key, it then updates the record. A key should be define first but in your case, you can directly execute the statement since you have mentioned that foo is already unique.

using INSERT INTO...SELECT you can combine INSERT..ON DUPLICATE UPDATE,

INSERT INTO YourExistingTable (Foo, Bar) 
SELECT Foo, Bar
FROM   TempTable
ON DUPLICATE KEY UPDATE Bar = VALUES(Bar) + Bar;

• the records will be combined after you have executed the statement. You can now drop the temporary table.

dropping temporary table,

DROP TABLE TempTable