SQL Server 2000：有条件的旋转

Question

我四处搜索但找不到类似的答案。

在排除 NULL 和 'NA' 字符串的条件下，在 SQL Server 2000 中推荐的最佳转换方法是什么？

我想从这个开始（select 只有 order_id = 100 和 line_no = 1）：

+----------+---------+-----+------+-----+------+----+
| order_id | line_no |  a  |  b   |  c  |  d   | e  |
+----------+---------+-----+------+-----+------+----+
|      100 |       1 | 123 | NULL | NA  | 456  | X1 |
|      101 |       1 | 789 | NA   | 123 | NULL | BB |
+----------+---------+-----+------+-----+------+----+

为此：

+----------+---------+------+--------+
| order_id | line_no | type | config |
+----------+---------+------+--------+
|      100 |       1 | a    | 123    |
|      100 |       1 | d    | 456    |
|      100 |       1 | e    | X1     |
+----------+---------+------+--------+

Answer 1

在SQL Server 2000 中，可用的选项不多。您可以为此使用 UNION ALL：

SELECT 'a' AS type, a
FROM mytable
WHERE a IS NOT NULL AND a <> 'NA'

UNION ALL 

SELECT 'b' AS type, b
FROM mytable
WHERE b IS NOT NULL AND b <> 'NA'

UNION ALL 

SELECT 'c' AS type, c
FROM mytable
WHERE c IS NOT NULL AND c <> 'NA'

UNION ALL 

SELECT 'd' AS type, d
FROM mytable
WHERE d IS NOT NULL AND d <> 'NA'

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