allow aliasing a la the postgres extension

Author: maxcountryman

src/parser.rs

@@ -526,7 +526,13 @@ impl Parser {
         // Note that PostgreSQL allows omitting the qualifier, so we provide
         // this more general implemenation.
         let leading_field = match self.peek_token() {
-            Some(Token::Word(..)) => Some(self.parse_date_time_field()?),
+            Some(Token::Word(kw))
+                if ["YEAR", "MONTH", "DAY", "HOUR", "MINUTE", "SECOND"]
+                    .iter()
+                    .any(|d| kw.keyword == *d) =>
+            {
+                Some(self.parse_date_time_field()?)
+            }
             _ => None,
         };
 

tests/sqlparser_common.rs

@@ -1558,6 +1558,11 @@ fn parse_literal_interval() {
     verified_only_select("SELECT INTERVAL '1' HOUR TO SECOND");
     verified_only_select("SELECT INTERVAL '1' MINUTE TO SECOND");
     verified_only_select("SELECT INTERVAL '1 YEAR'");
+    verified_only_select("SELECT INTERVAL '1 YEAR' AS one_year");
+    one_statement_parses_to(
+        "SELECT INTERVAL '1 YEAR' one_year",
+        "SELECT INTERVAL '1 YEAR' AS one_year",
+    );
 }
 
 #[test]