E051-09, “Rename columns in the FROM clause”

1. Only for values and select: FROM (VALUES | SELECT …) t(c1, c2)
2. Only for select: FROM (SELECT …) t(c1, c2)
3. Only for values, but then required: FROM (VALUES …) t(c1, c2)

Besides the tables names, the columns names can be renamed in the from and join clauses.

SELECT …
  FROM tbl_a [AS] a(a1, a2, …)
  JOIN tbl_b [AS] b(b1, b2, …)

This is typically used to assign names to column that don’t have a use-assigned name—such as columns produced by values or unnest:

SELECT b, a
  FROM (VALUES (1, 'a')
       ) t(a, b)

The SQL standard requires all columns to be renamed.

Extensions

Some systems allow renaming fewer columns as the table has so that only the first few columns are renamed.

Related

Tutorials

• Renaming Tables And Columns in the FROM Clause

Related Features

• E051-05, “Select list items can be renamed”

• E051-08, “Correlation names in the FROM clause”

Normative References

E051-09, “Rename columns in the FROM clause”, is an mandatory feature of ISO/IEC 9075-2:2023. The functionality first appeared in SQL:92 (intermediate).0 It became mandatory in 1999.