我有一个文件,其中可以包含 3 到 4 列用逗号分隔的数值。空字段定义为例外,当它们位于行尾时:
1,2,3,4,5 1,2,3,,5 1,2,3
下表是在 MySQL 中创建的:
+-------+--------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------+------+-----+---------+-------+ | one | int(1) | YES | | NULL | | | two | int(1) | YES | | NULL | | | three | int(1) | YES | | NULL | | | four | int(1) | YES | | NULL | | | five | int(1) | YES | | NULL | | +-------+--------+------+-----+---------+-------+
我正在尝试使用 MySQL LOAD 命令加载数据:
LOAD DATA INFILE '/tmp/testdata.txt' INTO TABLE moo FIELDS TERMINATED BY "," LINES TERMINATED BY "\n";
结果表:
+------+------+-------+------+------+ | one | two | three | four | five | +------+------+-------+------+------+ | 1 | 2 | 3 | 4 | 5 | | 1 | 2 | 3 | 0 | 5 | | 1 | 2 | 3 | NULL | NULL | +------+------+-------+------+------+
问题在于,当原始数据中的字段为空且未定义时,MySQL 出于某种原因不使用列默认值(即 NULL)并使用零。当字段全部丢失时,正确使用 NULL。
不幸的是,在这个阶段我必须能够区分 NULL 和 0,所以任何帮助都将不胜感激。
谢谢S。
编辑
显示警告的输出:
+---------+------+--------------------------------------------------------+ | Level | Code | Message | +---------+------+--------------------------------------------------------+ | Warning | 1366 | Incorrect integer value: '' for column 'four' at row 2 | | Warning | 1261 | Row 3 doesn't contain data for all columns | | Warning | 1261 | Row 3 doesn't contain data for all columns | +---------+------+--------------------------------------------------------+
这将做你想要的。它将第四个字段读入局部变量,然后将实际字段值设置为 NULL,如果局部变量最终包含一个空字符串:
LOAD DATA INFILE '/tmp/testdata.txt' INTO TABLE moo FIELDS TERMINATED BY "," LINES TERMINATED BY "\n" (one, two, three, @vfour, five) SET four = NULLIF(@vfour,'') ;
如果它们都可能为空,那么您会将它们全部读入变量并具有多个 SET 语句,如下所示:
LOAD DATA INFILE '/tmp/testdata.txt' INTO TABLE moo FIELDS TERMINATED BY "," LINES TERMINATED BY "\n" (@vone, @vtwo, @vthree, @vfour, @vfive) SET one = NULLIF(@vone,''), two = NULLIF(@vtwo,''), three = NULLIF(@vthree,''), four = NULLIF(@vfour,'') ;