Question

我有一张有价值观的表格。我正在尝试创建一个新列，其行值将取决于现有列的行。例如，在下表中，如果从索引6到索引7的id列的substr大于10，那么该行的新列的值应该是索引1-4处的id的子字符串< em>连字符 substr（id，1,4）+1。否则值应为substr（id，1,4）-1 连字符 substr（id，1,4）。

id          New Column  Name
M20061012   2006-2007   Jude
K20070212   2006-2007   Anne
D20071214   2007-2008   John

以下是表格每一行的算法：

if substr(id, 5, 1) < 10
   New Column value at that row = substr(id, 1, 4) - substr(id, 1, 4)+1
else
   New Column value at that row = substr(id, 1, 4)-1 - substr(id, 1, 4)

任何帮助将不胜感激感谢

修改所以我按照@scwagner

的建议尝试了这个

SELECT
id,
(CASE WHEN CONVERT(SUBSTR(id,6,2), SIGNED) < 10 
THEN CONCAT(CONVERT(SUBSTR(id, 2, 4),SIGNED)-1,'-',CONVERT(SUBSTR(id, 2, 4),SIGNED)) 
ELSE CONCAT(CONVERT(SUBSTR(id, 2, 4),SIGNED),'-',CONVERT(SUBSTR(id, 2, 4),SIGNED)+1)   END) AS `New Column`,
Name
FROM new

其中new是表的名称。但是这会返回一个包含所有行值= BLOB的列。我该如何解决这个问题？

Answer 1

您可能希望在更多数据上对此进行测试，但这适用于MySQL 5.1.41-3ubuntu12.8以及您提供的测试数据：

SELECT
  id,
  (CASE WHEN CONVERT(SUBSTR(id,6,2), SIGNED) < 10 THEN CONCAT(CONVERT(SUBSTR(id, 2, 4),SIGNED)-1,'-',CONVERT(SUBSTR(id, 2, 4),SIGNED)) ELSE CONCAT(CONVERT(SUBSTR(id, 2, 4),SIGNED),'-',CONVERT(SUBSTR(id, 2, 4),SIGNED)+1) END) AS `New Column`,
  Name
FROM
  <your table>

Answer 2

想出来：

 SELECT
    id,
    (CASE WHEN CONVERT(SUBSTR(id,6,2), SIGNED) < 10 
    THEN CONCAT(CAST(CONVERT(SUBSTR(id, 2, 4),SIGNED)-1 AS CHAR),'-',CAST(CONVERT(SUBSTR(id, 2, 4),SIGNED) AS CHAR)) 
    ELSE CONCAT(CAST(CONVERT(SUBSTR(id, 2, 4),SIGNED) AS CHAR),'-',CAST(CONVERT(SUBSTR(id, 2, 4),SIGNED)+1) AS CHAR)   END) AS `New Column`,
    Name
    FROM new

MySql使用现有列创建和填充新列

2 个答案: