Add DROP TRIGGER support for SQL Server (apache#1813)

Author: aharpervc

src/parser/mod.rs

@@ -5177,7 +5177,7 @@ impl<'a> Parser<'a> {
     /// DROP TRIGGER [ IF EXISTS ] name ON table_name [ CASCADE | RESTRICT ]
     /// ```
     pub fn parse_drop_trigger(&mut self) -> Result<Statement, ParserError> {
-        if !dialect_of!(self is PostgreSqlDialect | GenericDialect | MySqlDialect) {
+        if !dialect_of!(self is PostgreSqlDialect | GenericDialect | MySqlDialect | MsSqlDialect) {
             self.prev_token();
             return self.expected("an object type after DROP", self.peek_token());
         }

tests/sqlparser_mssql.rs

@@ -2038,3 +2038,18 @@ fn parse_mssql_merge_with_output() {
         OUTPUT $action, deleted.ProductID INTO dsi.temp_products";
     ms_and_generic().verified_stmt(stmt);
 }
+
+#[test]
+fn parse_drop_trigger() {
+    let sql_drop_trigger = "DROP TRIGGER emp_stamp;";
+    let drop_stmt = ms().one_statement_parses_to(sql_drop_trigger, "");
+    assert_eq!(
+        drop_stmt,
+        Statement::DropTrigger {
+            if_exists: false,
+            trigger_name: ObjectName::from(vec![Ident::new("emp_stamp")]),
+            table_name: None,
+            option: None,
+        }
+    );
+}