MySQL "LOAD DATA INFILE" 正在将未加引号的 "NULL" 字符串导入为“NULL”

Question

我正在使用 MySQL 5.7.35。如果我在 CSV 文件上使用 LOAD DATA INFILE 命令并将 NULL 作为 CSV 文件中未加引号的字符串值，则该值将导入为 MySQL.

中的 NULL

例如，如果我导入一个包含以下内容的 CSV 文件：

record_number,a,b,c,d,e,f
1,1,2,3,4,5,6
2,NULL,null,Null,nUlL,,"NULL"

导入的 table 将具有以下值：

+---------------+------+--------+--------+--------+--------+--------+
| record_number | a    | b      | c      | d      | e      | f      |
+---------------+------+--------+--------+--------+--------+--------+
|             1 | 1    | 2      | 3      | 4      | 5      | 6      |
|             2 | NULL | "null" | "Null" | "nUlL" | ""     | "NULL" |
+---------------+------+--------+--------+--------+--------+--------+

有没有办法在不修改 CSV 文件的情况下强制将 a 列记录 2 作为字符串导入？

更新

@Barmar 指出 MySQL 文档中有一段是关于此行为的 here:

If FIELDS ENCLOSED BY is not empty, a field containing the literal word NULL as its value is read as a NULL value. This differs from the word NULL enclosed within FIELDS ENCLOSED BY characters, which is read as the string 'NULL'.

Answer 1

这已记录在案 here:

If FIELDS ENCLOSED BY is not empty, a field containing the literal word NULL as its value is read as a NULL value. This differs from the word NULL enclosed within FIELDS ENCLOSED BY characters, which is read as the string 'NULL'.

所以你需要用FIELDS ENCLOSED BY '"'之类的东西指定引号，然后在CSV文件中写"NULL"。

您可以检查代码中的 NULL 值并将其转换为字符串。

LOAD DATA INFILE 'file.txt'
  INTO TABLE t1
  (record_number, @a, @b, @c, @d, @e, @f)
  SET a = IFNULL(@a, 'NULL'),
      b = IFNULL(@b, 'NULL'),
      c = IFNULL(@c, 'NULL'),
      d = IFNULL(@d, 'NULL'),
      e = IFNULL(@e, 'NULL'),
      f = IFNULL(@f, 'NULL')

但是，这无法区分将 NULL 写成 \N 和 MySQL 将 NULL 视为 NULL.

MySQL "LOAD DATA INFILE" 正在将未加引号的 "NULL" 字符串导入为“NULL”

MySQL "LOAD DATA INFILE" is importing unquoted "NULL" string as `NULL`

mysql

csv

null