LOAD DATA from CSV file where doublequote was used as the escape character

Question

I have a bunch of CSV data that I need to load into a MySQL database. Well, CSV-ish, perhaps. (edit: actually, it looks like the stuff described in RFC 4180)

Each row is a list of comma-separated doublequoted strings. To escape any doublequotes that appear within a column value, double doublequotes are used. Backslashes are allowed to represent themselves.

For example, the line:

"", "\wave\", ""hello,"" said the vicar", "what are ""scare-quotes"" good for?", "I'm reading ""Bossypants"""

if parsed into JSON should be:

[ "", "\\wave\\", "\"hello,\" said the vicar", "what are \"scare-quotes\" good for?", "I'm reading \"Bossypants\"" ]

I'm trying to use the LOAD DATA to read the CSV in, but I'm running into some weird behaviour.

---

As an example, consider if I have a simple two column table

shell% mysql exampledb -e "describe person"
+-------+-----------+------+-----+---------+-------+
| Field | Type      | Null | Key | Default | Extra |
+-------+-----------+------+-----+---------+-------+
| ID    | int(11)   | YES  |     | NULL    |       |
| UID   | char(255) | YES  |     | NULL    |       |
+-------+-----------+------+-----+---------+-------+
shell%

If the first non-header line of my input file ends on "":

shell% cat temp-1.csv
"ID","UID"
"9",""
"0","Steve the Pirate"
"1","\Alpha"
"2","Hoban ""Wash"" Washburne"
"3","Pastor Veal"
"4","Tucker"
"10",""
"5","Simon"
"6","Sonny"
"7","Wat\"

I can either load every non-header line but the first:

mysql> DELETE FROM person;
Query OK, 0 rows affected (0.00 sec)

mysql> LOAD DATA
          LOCAL INFILE 'temp-1.csv'
          INTO TABLE person
          FIELDS
            TERMINATED BY ','
            ENCLOSED BY '"'
            ESCAPED BY '"'
          LINES
            TERMINATED BY '\n'
          IGNORE 1 LINES
       ;
Query OK, 9 rows affected (0.00 sec)
Records: 9  Deleted: 0  Skipped: 0  Warnings: 0

mysql> SELECT * FROM person;
+------+------------------------+
| ID   | UID                    |
+------+------------------------+
|    0 | Steve the Pirate       |
|   10 |                        |
|    1 | \Alpha                 |
|    2 | Hoban "Wash" Washburne |
|    3 | Pastor Veal            |
|    4 | Tucker                 |
|    5 | Simon                  |
|    6 | Sonny                  |
|    7 | Wat\                   |
+------+------------------------+
9 rows in set (0.00 sec)

Or I can load all lines including the header:

mysql> DELETE FROM person;
Query OK, 9 rows affected (0.00 sec)

mysql> LOAD DATA
          LOCAL INFILE 'temp-1.csv'
          INTO TABLE person
          FIELDS
            TERMINATED BY ','
            ENCLOSED BY '"'
            ESCAPED BY '"'
          LINES
            TERMINATED BY '\n'
          IGNORE 0 LINES
       ;
Query OK, 11 rows affected, 1 warning (0.01 sec)
Records: 11  Deleted: 0  Skipped: 0  Warnings: 1

mysql> show warnings;
+---------+------+--------------------------------------------------------+
| Level   | Code | Message                                                |
+---------+------+--------------------------------------------------------+
| Warning | 1366 | Incorrect integer value: 'ID' for column 'ID' at row 1 |
+---------+------+--------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT * FROM person;
+------+------------------------+
| ID   | UID                    |
+------+------------------------+
|    0 | UID                    |
|    9 |                        |
|    0 | Steve the Pirate       |
|   10 |                        |
|    1 | \Alpha                 |
|    2 | Hoban "Wash" Washburne |
|    3 | Pastor Veal            |
|    4 | Tucker                 |
|    5 | Simon                  |
|    6 | Sonny                  |
|    7 | Wat\                   |
+------+------------------------+
11 rows in set (0.00 sec)

If no lines of my input file end on "":

shell% cat temp-2.csv
"ID","UID"
"0","Steve the Pirate"
"1","\Alpha"
"2","Hoban ""Wash"" Washburne"
"3","Pastor Veal"
"4","Tucker"
"5","Simon"
"6","Sonny"
"7","Wat\"

then I can either load no lines:

mysql> DELETE FROM person;
Query OK, 11 rows affected (0.00 sec)

mysql> LOAD DATA
          LOCAL INFILE 'temp-2.csv'
          INTO TABLE person
          FIELDS
            TERMINATED BY ','
            ENCLOSED BY '"'
            ESCAPED BY '"'
          LINES
            TERMINATED BY '\n'
          IGNORE 1 LINES
       ;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Deleted: 0  Skipped: 0  Warnings: 0

mysql> SELECT * FROM person;
Empty set (0.00 sec)

Or I can load all the lines including the header:

mysql> DELETE FROM person;
Query OK, 0 rows affected (0.00 sec)

mysql> LOAD DATA
          LOCAL INFILE 'temp-2.csv'
          INTO TABLE person
          FIELDS
            TERMINATED BY ','
            ENCLOSED BY '"'
            ESCAPED BY '"'
          LINES
            TERMINATED BY '\n'
          IGNORE 0 LINES
       ;
Query OK, 9 rows affected, 1 warning (0.03 sec)
Records: 9  Deleted: 0  Skipped: 0  Warnings: 1

mysql> show warnings;
+---------+------+--------------------------------------------------------+
| Level   | Code | Message                                                |
+---------+------+--------------------------------------------------------+
| Warning | 1366 | Incorrect integer value: 'ID' for column 'ID' at row 1 |
+---------+------+--------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT * FROM person;
+------+------------------------+
| ID   | UID                    |
+------+------------------------+
|    0 | UID                    |
|    0 | Steve the Pirate       |
|    1 | \Alpha                 |
|    2 | Hoban "Wash" Washburne |
|    3 | Pastor Veal            |
|    4 | Tucker                 |
|    5 | Simon                  |
|    6 | Sonny                  |
|    7 | Wat\                   |
+------+------------------------+
9 rows in set (0.00 sec)

So now that I've discovered many ways to do it wrong, how can I use LOAD DATA to import the data from these files into my database?

Answer 1

According to the documentation for LOAD DATA, treating doubled double quotes as a double quote is the default:

If the field begins with the ENCLOSED BY character, instances of that character are recognized as terminating a field value only if followed by the field or line TERMINATED BY sequence. To avoid ambiguity, occurrences of the ENCLOSED BY character within a field value can be doubled and are interpreted as a single instance of the character. For example, if ENCLOSED BY '"' is specified, quotation marks are handled as shown here:

"The ""BIG"" boss"  -> The "BIG" boss
The "BIG" boss      -> The "BIG" boss
The ""BIG"" boss    -> The ""BIG"" boss

So all I need to do is disable interpreting \ as an escape character, by using ESCAPED BY ''.

LOAD DATA
  LOCAL INFILE 'temp-1.csv'
  INTO TABLE person
  FIELDS
    TERMINATED BY ','
    ENCLOSED BY '"'
    ESCAPED BY ''
  LINES
    TERMINATED BY '\n'
  IGNORE 1 LINES
;