Guard insert table aliases with an explicit dialect flag

Author: xitep

src/dialect/mod.rs

@@ -1238,6 +1238,17 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns true if this dialect supports `INSERT INTO t AS alias ...`.
+    fn supports_insert_table_explicit_alias(&self) -> bool {
+        false
+    }
+
+    /// Returns true if this dialect supports `INSERT INTO t alias ...` with
+    /// `alias` _not_ preceded by the "AS" keyword.
+    fn supports_insert_table_implicit_alias(&self) -> bool {
+        false
+    }
+
     /// Returns true if this dialect supports `SET` statements without an explicit
     /// assignment operator such as `=`. For example: `SET SHOWPLAN_XML ON`.
     fn supports_set_stmt_without_operator(&self) -> bool {

src/dialect/oracle.rs

@@ -110,4 +110,11 @@ impl Dialect for OracleDialect {
     fn supports_comment_optimizer_hint(&self) -> bool {
         true
     }
+
+    /// Supports insert table aliases (but with no preceding "AS" keyword)
+    ///
+    /// See <https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/INSERT.html#GUID-903F8043-0254-4EE9-ACC1-CB8AC0AF3423__GUID-AC239E95-0DD5-4F4B-A849-55C87840D0E6>
+    fn supports_insert_table_implicit_alias(&self) -> bool {
+        true
+    }
 }

src/dialect/postgresql.rs

@@ -288,4 +288,10 @@ impl Dialect for PostgreSqlDialect {
     fn supports_interval_options(&self) -> bool {
         true
     }
+
+    /// [Postgres] support insert table aliases with an explicit "AS" keyword.
+    /// See: <https://www.postgresql.org/docs/17/sql-insert.html>
+    fn supports_insert_table_explicit_alias(&self) -> bool {
+        true
+    }
 }

src/parser/mod.rs

@@ -17133,19 +17133,15 @@ impl<'a> Parser<'a> {
             let table = self.parse_keyword(Keyword::TABLE);
             let table_object = self.parse_table_object()?;
 
-            let table_alias = if dialect_of!(self is OracleDialect) {
-                if !self.peek_sub_query()
-                    && self.peek_one_of_keywords(&[Keyword::DEFAULT, Keyword::VALUES]).is_none()
-                {
+            let table_alias = if self.dialect.supports_insert_table_implicit_alias()
+                && !self.peek_sub_query()
+                && self.peek_one_of_keywords(&[Keyword::AS, Keyword::DEFAULT, Keyword::VALUES]).is_none() {
                     self.maybe_parse(|parser| parser.parse_identifier())?
                         .map(|alias| TableAliasWithoutColumns {
                             explicit: false,
                             alias,
                         })
-                } else {
-                    None
-                }
-            } else if dialect_of!(self is PostgreSqlDialect) && self.parse_keyword(Keyword::AS) {
+            } else if self.dialect.supports_insert_table_explicit_alias() && self.parse_keyword(Keyword::AS) {
                 Some(TableAliasWithoutColumns {
                     explicit: true,
                     alias: self.parse_identifier()?,

tests/sqlparser_oracle.rs

@@ -483,6 +483,15 @@ fn test_insert_without_alias() {
         ))
     );
 
+    // check AS
+    let sql = "INSERT INTO AS t default SELECT 'a' FROM dual";
+    assert_eq!(
+        oracle_dialect.parse_sql_statements(sql),
+        Err(ParserError::ParserError(
+            "Expected: SELECT, VALUES, or a subquery in the query body, found: default".into()
+        ))
+    );
+
     // check SELECT
     let sql = "INSERT INTO t SELECT 'a' FROM dual";
     let stmt = oracle_dialect.verified_stmt(sql);