问题
I'm writing a query to do some stuff. But its not working the way I want it to:
select CORR_ID from TABLE1
where CORR_ID not in (select id from TABLE2)
The problem is, TABLE2.id is a long, while TABLE1.CORR_ID is a string.
So how can I make it work?
PS: I'm using IBM UDB.
回答1:
Okay, I found a method:
select CORR_ID from TABLE1 where CORR_ID not in
(select CAST( CAST(id AS CHAR(50)) AS VARCHAR(50) ) from TABLE2)
This is pretty intriguing: You can't cast a BIGINT to VARCHAR, but:
- you can cast a BIGINT to CHAR
- and you can cast a CHAR TO VARCHAR
this is ridiculous!
回答2:
DB2 allows a VARCHAR and CHAR column to be compared without additional casting, so all you really need to do is cast the number.
SELECT corr_id FROM table1 WHERE corr_id NOT IN (SELECT CHAR( id ) FROM table2 )
回答3:
You should be able to cast the selected id column to match the data type of corr_id
select CORR_ID from TABLE1 where CORR_ID not in (select cast(id as varchar) from TABLE2)
来源：https://stackoverflow.com/questions/1038670/datatype-conversion-in-ibm-db2-bigint-to-varchar