Mysql – How to import CSV file into a MySQL table

csvload-data-infileMySQL

I have an unnormalized events-diary CSV from a client that I'm trying to load into a MySQL table so that I can refactor into a sane format. I created a table called 'CSVImport' that has one field for every column of the CSV file. The CSV contains 99 columns , so this was a hard enough task in itself:

CREATE TABLE 'CSVImport' (id INT);
ALTER TABLE CSVImport ADD COLUMN Title VARCHAR(256);
ALTER TABLE CSVImport ADD COLUMN Company VARCHAR(256);
ALTER TABLE CSVImport ADD COLUMN NumTickets VARCHAR(256);
...
ALTER TABLE CSVImport Date49 ADD COLUMN Date49 VARCHAR(256);
ALTER TABLE CSVImport Date50 ADD COLUMN Date50 VARCHAR(256);

No constraints are on the table, and all the fields hold VARCHAR(256) values, except the columns which contain counts (represented by INT), yes/no (represented by BIT), prices (represented by DECIMAL), and text blurbs (represented by TEXT).

I tried to load data into the file:

LOAD DATA INFILE '/home/paul/clientdata.csv' INTO TABLE CSVImport;
Query OK, 2023 rows affected, 65535 warnings (0.08 sec)
Records: 2023  Deleted: 0  Skipped: 0  Warnings: 198256
SELECT * FROM CSVImport;
| NULL             | NULL        | NULL           | NULL | NULL               | 
...

The whole table is filled with NULL.

I think the problem is that the text blurbs contain more than one line, and MySQL is parsing the file as if each new line would correspond to one databazse row. I can load the file into OpenOffice without a problem.

The clientdata.csv file contains 2593 lines, and 570 records. The first line contains column names. I think it is comma delimited, and text is apparently delimited with doublequote.

UPDATE:

When in doubt, read the manual: http://dev.mysql.com/doc/refman/5.0/en/load-data.html

I added some information to the LOAD DATA statement that OpenOffice was smart enough to infer, and now it loads the correct number of records:

LOAD DATA INFILE "/home/paul/clientdata.csv"
INTO TABLE CSVImport
COLUMNS TERMINATED BY ','
OPTIONALLY ENCLOSED BY '"'
ESCAPED BY '"'
LINES TERMINATED BY '\n'
IGNORE 1 LINES;

But still there are lots of completely NULL records, and none of the data that got loaded seems to be in the right place.

Best Answer

Use mysqlimport to load a table into the database:

mysqlimport --ignore-lines=1 \
            --fields-terminated-by=, \
            --local -u root \
            -p Database \
             TableName.csv

I found it at http://chriseiffel.com/everything-linux/how-to-import-a-large-csv-file-to-mysql/

To make the delimiter a tab, use --fields-terminated-by='\t'

Related Solutions

Sql – How to concatenate text from multiple rows into a single text string in SQL Server

If you are on SQL Server 2017 or Azure, see Mathieu Renda answer.

I had a similar issue when I was trying to join two tables with one-to-many relationships. In SQL 2005 I found that XML PATH method can handle the concatenation of the rows very easily.

If there is a table called STUDENTS

SubjectID       StudentName
----------      -------------
1               Mary
1               John
1               Sam
2               Alaina
2               Edward

Result I expected was:

SubjectID       StudentName
----------      -------------
1               Mary, John, Sam
2               Alaina, Edward

I used the following T-SQL:

SELECT Main.SubjectID,
       LEFT(Main.Students,Len(Main.Students)-1) As "Students"
FROM
    (
        SELECT DISTINCT ST2.SubjectID, 
            (
                SELECT ST1.StudentName + ',' AS [text()]
                FROM dbo.Students ST1
                WHERE ST1.SubjectID = ST2.SubjectID
                ORDER BY ST1.SubjectID
                FOR XML PATH ('')
            ) [Students]
        FROM dbo.Students ST2
    ) [Main]

You can do the same thing in a more compact way if you can concat the commas at the beginning and use substring to skip the first one so you don't need to do a sub-query:

SELECT DISTINCT ST2.SubjectID, 
    SUBSTRING(
        (
            SELECT ','+ST1.StudentName  AS [text()]
            FROM dbo.Students ST1
            WHERE ST1.SubjectID = ST2.SubjectID
            ORDER BY ST1.SubjectID
            FOR XML PATH ('')
        ), 2, 1000) [Students]
FROM dbo.Students ST2

Mysql – concatenate multiple MySQL rows into one field

You can use GROUP_CONCAT:

SELECT person_id,
   GROUP_CONCAT(hobbies SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;

As Ludwig stated in his comment, you can add the DISTINCT operator to avoid duplicates:

SELECT person_id,
   GROUP_CONCAT(DISTINCT hobbies SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;

As Jan stated in their comment, you can also sort the values before imploding it using ORDER BY:

SELECT person_id, 
       GROUP_CONCAT(hobbies ORDER BY hobbies ASC SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;

As Dag stated in his comment, there is a 1024 byte limit on the result. To solve this, run this query before your query:

SET group_concat_max_len = 2048;

Of course, you can change 2048 according to your needs. To calculate and assign the value:

SET group_concat_max_len = CAST(
                     (SELECT SUM(LENGTH(hobbies)) + COUNT(*) * LENGTH(', ')
                           FROM peoples_hobbies
                           GROUP BY person_id) AS UNSIGNED);

Best Answer

Related Solutions

Sql – How to concatenate text from multiple rows into a single text string in SQL Server

Mysql – concatenate multiple MySQL rows into one field

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