DB2:不允许“NULL"；柱子? [英] DB2: Won't Allow "NULL" column?

问题描述

我们的应用正在运行的复杂查询的一部分包含以下行:...(内部查询)

Part of a complex query that our app is running contains the lines: ...(inner query)

SELECT
...
NULL as column_A,
NULL as column_B,
...
FROM
...

虽然在 MSSQL 和 Oracle DBs 中完全可以，但这种创建具有 null 值的列的语法在 DB2 中是不允许的.从技术上讲，我可以将其更改为:

This syntax of creating columns with null values is not allowed in DB2 altough it is totally OK in MSSQL and Oracle DBs. Technically I can change it to:

'' as column_A,
'' as column_B, 

但这并没有完全相同的含义，可能会损坏我们的计算结果.如何使用其他语法在 DB2 中创建具有空值的列??

But this doesn't have exactly the same meaning and can damage our calculation results. How can I create columns with null values in DB2 using other syntax??

推荐答案

DB2是强类型的，所以你需要告诉DB2你的NULL是什么类型的列:

DB2 is strongly typed, so you need to tell DB2 what kind of column your NULL is:

select 
   ...
   cast(NULL as int) as column_A,
   cast(NULL as varchar(128)) as column_B,
   ...
FROM
   ...

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