MySQL:如何将一个值分成 3 个可能的部分(除以空格)

Question

我有一个列，可以由空格分隔 1、2 或 3 个部分。 我需要提取每个部分“如果”它存在(字符串将始终包含至少第一部分)。

示例:

1: Apple
2: Apple Orange
3: Apple Pear lemon


|1| Apple             | Apple |        |        |
|2| Apple Orange      | Apple | Orange |        |
|3| Pear lemon Orange | Pear  | lemon  | Orange |

我可以提取第一部分和第三部分 (但如果只有一个部分，这会在第三列中插入相同的值)。

SELECT
`productCode`,
SUBSTRING_INDEX( `productCode`, ' ', 1 ),
SUBSTRING_INDEX( `productCode`, ' ', -1 )
FROM tblSubmissionProducts;

Answer 1

您可以使用它来分割字符串:

SELECT 
  REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 1)),' ',1)) AS n1,
  REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 2)),' ',1)) AS n2,
  REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 3)),' ',1)) AS n3,
  REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 4)),' ',1)) AS n4;

示例

MariaDB [(none)]> SELECT
    ->   REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 1)),' ',1)) AS n1,
    ->   REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 2)),' ',1)) AS n2,
    ->   REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 3)),' ',1)) AS n3,
    ->   REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX('This is a Test', ' ', 4)),' ',1)) AS n4;
+------+----+----+------+
| n1   | n2 | n3 | n4   |
+------+----+----+------+
| This | is | a  | Test |
+------+----+----+------+
1 row in set (0.00 sec)

MariaDB [(none)]>

更改了答案

SELECT 
  TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 1)),' ',1))) AS n1,
  TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 2)),' ',1))) AS n2,
  TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 3)),' ',1))) AS n1;  

更好的示例

MariaDB [(none)]> SELECT
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 1)),' ',1))) AS n1,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 2)),' ',1))) AS n2,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple', '    '), ' ', 3)),' ',1))) AS n1;
+-------+----+----+
| n1    | n2 | n1 |
+-------+----+----+
| Apple |    |    |
+-------+----+----+
1 row in set (0.00 sec)

MariaDB [(none)]>
MariaDB [(none)]> SELECT
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple Orange', '    '), ' ', 1)),' ',1))) AS n1,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple Orange', '    '), ' ', 2)),' ',1))) AS n2,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Apple Orange', '    '), ' ', 3)),' ',1))) AS n1;
+-------+--------+----+
| n1    | n2     | n1 |
+-------+--------+----+
| Apple | Orange |    |
+-------+--------+----+
1 row in set (0.00 sec)

MariaDB [(none)]>
MariaDB [(none)]> SELECT
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Pear lemon Orange', '    '), ' ', 1)),' ',1))) AS n1,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Pear lemon Orange', '    '), ' ', 2)),' ',1))) AS n2,
    ->   TRIM(REVERSE(SUBSTRING_INDEX(REVERSE (SUBSTRING_INDEX(CONCAT('Pear lemon Orange', '    '), ' ', 3)),' ',1))) AS n1;
+------+-------+--------+
| n1   | n2    | n1     |
+------+-------+--------+
| Pear | lemon | Orange |
+------+-------+--------+
1 row in set (0.00 sec)

MariaDB [(none)]>