Question

For example

SELECT (SELECT col_name FROM column_names WHERE col_id = 1) FROM my_table

It returns the value of col_name instead of the value of table.col_name
e.g. if col_name is x1 then the above select will return “x1” instead of the value of SELECT x1 FROM my_table

Is there a way to do it in

• Microsoft SQL Sever 2008? (based on the answers, seems that yes)
• Oracle 11g?

If it is, how can I use the select clause columns in a where clause without repeating the subselect?

Answer 1

In SQL Server you can use dynamic SQL, something like this:

declare @TableName sysname = quotename('Test')

declare @ColumnList varchar(max)

select @ColumnList = isnull(@ColumnList + ', ', '') + quotename(name)
from sys.columns
where object_name(object_id) = @TableName

declare @SqlCommand varchar(max) = 'select ' + @ColumnList + ' from ' + @TableName 
execute(@SqlCommand)