SQL查询-将数据类型varchar转换为数值

Question

I have an issue converting pricing in a SQL query:

CASE CAST(R.Price AS decimal(10,2)) 
   WHEN 'NULL' 
      THEN '0'
END AS 'PricePoint',

Unfortunately, it throws this error:

Error converting data type varchar to numeric.

Thanks for the help.

Answer 1

You are comparing NULL as Varchar so it is giving error.

Use the below query

CASE CAST(R.Price AS decimal(10,2)) WHEN NULL THEN '0'END AS 'PricePoint',

Answer 2

If this is for SQL Server , then you must use this code to use the IS NULL checks (and not the "normal" equality operators):

CASE 
   WHEN CAST(R.Price AS decimal(10, 2)) IS NULL
      THEN '0'
END AS 'PricePoint',

Also: if you want to return a numerical value of 0 , you should again forget about the single quotes around the value - putting it in single quotes is returning a string value (instead of an int ):

CASE 
   WHEN CAST(R.Price AS decimal(10, 2)) IS NULL
      THEN 0
END AS 'PricePoint',

Update: if you want to return the regular prices for anything that is not NULL , add a ELSE clause to your CASE :

CASE 
   WHEN CAST(R.Price AS decimal(10, 2)) IS NULL
      THEN 0
      ELSE CAST(R.Price AS decimal(10, 2)) 
END AS 'PricePoint',