inserting data from one table to another after casting the values

Question

I have a #temp table containing all the data that needs to be inserted into a table named Customer. The column names of the two tables are exactly the same, but the data types are different. So I need to cast from one type to another before inserting the data into the Customer table.

The solution has to be implemented for a dynamic condition. i.e, I don't know the column name or data type.

Answer 1

DECLARE @SQL varchar(8000)


SET @SQL = ''

SELECT @SQL = @SQL +  ' CAST(' + COLUMN_NAME + ' as ' + ISNULL(DATA_TYPE + '(' + CAST(CHARACTER_OCTET_LENGTH as varchar(20)) + ') )','') + ' as ' + COLUMN_NAME + ','  FROM INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'YourPermTable'

SET @SQL = SUBSTRING(@SQL,1,LEN(@SQL)-1)

SET @SQL = 'SELECT ' + @SQL + ' FROM YourTempTable'


PRINT @SQL  

Add the insert part and it should do the trick!

Answer 2

I would be writing some code to do this, I'm not sure whether it would be achievable using purely SQL. You'd need to dynamically create a (or some) SQL statements, which may be a question for the chaps over in the programming section, however:

SELECT DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'tablename' AND COLUMN_NAME = 'columnname'

Would give you the datatype; you could then select the data from your other table and cast it to the datatype, you can also pull column_name from information_schema but without a table name.. That's another question!