diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml
index 95559ef1ac..47e6369f1a 100644
--- a/doc/src/sgml/queries.sgml
+++ b/doc/src/sgml/queries.sgml
@@ -588,8 +588,6 @@ SELECT * FROM my_table AS m WHERE my_table.a > 5; -- wrong
SELECT * FROM people AS mother JOIN people AS child ON mother.id = child.mother_id;
- Additionally, an alias is required if the table reference is a
- subquery (see ).
@@ -639,9 +637,9 @@ SELECT a.* FROM (my_table AS a JOIN your_table AS b ON ...) AS c
Subqueries specifying a derived table must be enclosed in
- parentheses and must be assigned a table
- alias name (as in ). For
- example:
+ parentheses. They may be assigned a table alias name, and optionally
+ column alias names (as in ).
+ For example:
FROM (SELECT * FROM table1) AS alias_name
@@ -660,10 +658,18 @@ FROM (SELECT * FROM table1) AS alias_name
FROM (VALUES ('anne', 'smith'), ('bob', 'jones'), ('joe', 'blow'))
AS names(first, last)
- Again, a table alias is required. Assigning alias names to the columns
+ Again, a table alias is optional. Assigning alias names to the columns
of the VALUES list is optional, but is good practice.
For more information see .
+
+
+ According to the SQL standard, a table alias name must be supplied
+ for a subquery. PostgreSQL
+ allows AS and the alias to be omitted, but
+ writing one is good practice in SQL code that might be ported to
+ another system.
+