Alternatives to USING in a JOIN for SQL Server for avoiding duplicated columns in joined table

Question

SQL Server does not offer the keyword USING in the context of a JOIN,
nor it provides a NATURAL JOIN.

Besides explicitly (manually) listing all the columns (link

Answer 1

It is not easy. But it is possible. Developing from this, you would first create two separated lists with all the columns of the 2 tables, excluding the common column on which you want to join:

DECLARE @columnsA varchar(8000)

SELECT @columnsA = ISNULL(@columnsA + ', ','') + QUOTENAME(column_name)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'tableA' AND COLUMN_NAME <> 'commonColumn'
ORDER BY ORDINAL_POSITION

DECLARE @columnsB varchar(8000)

SELECT @columnsB = ISNULL(@columnsB + ', ','') + QUOTENAME(column_name)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'tableB' AND COLUMN_NAME <> 'commonColumn'
ORDER BY ORDINAL_POSITION

Then you would use them for your query, selecting the commonColumn only for one of the table:

EXEC ('SELECT tableA.commonColumn, ' + @columnA + ', ' + @columnsB + ' FROM tableA INNER JOIN tableB ON tableA.commonColumn = tableB.commonColumn;')

So there's at least one way to do it. :) It is apparently also moderately efficient. I am not an SQL expert, but I suppose there is a way to create a function out of this, maybe one function to "select all columns but [...]" and one function that would do the join as USING would do.

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It becomes a little bit simpler if in listing we add also the containing table. In this way we need to extract only the column names from one table.

DECLARE @columnsB varchar(8000)

SELECT @columnsB = ISNULL(@columnsB + ', ','') + QUOTENAME(table_name) + '.' + QUOTENAME(column_name)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'tableB' AND COLUMN_NAME <> 'commonColumn'
ORDER BY ORDINAL_POSITION

And the query is modified into:

EXEC ('SELECT tableA.* ', ' + @columnsB + ' FROM tableA INNER JOIN tableB ON tableA.commonColumn = tableB.commonColumn;')