Improve MySQL CREATE TRIGGER parsing

MySQL uses a statement body similar to MSSQL (but without the `AS`
keyword) instead of `EXECUTE` body style used in Postgres and standard
SQL. But unlike MSSQL, MySQL puts the trigger period before the target
table. We add some flags to indicate these differences and allow parsing
and round tripping MySQL triggers. The main benefit is that we can now
handle MySQL triggers which include `BEGIN; ... END;` compound
statements.

Author: mvzink

src/ast/mod.rs

@@ -3962,6 +3962,15 @@ pub enum Statement {
         /// EXECUTE FUNCTION trigger_function();
         /// ```
         period: TriggerPeriod,
+        /// Whether the trigger period was specified before the target table name.
+        ///
+        /// ```sql
+        /// -- period_before_table == true: Postgres, MySQL, and standard SQL
+        /// CREATE TRIGGER t BEFORE INSERT ON table_name ...;
+        /// -- period_before_table == false: MSSQL
+        /// CREATE TRIGGER t ON table_name BEFORE INSERT ...;
+        /// ```
+        period_before_table: bool,
         /// Multiple events can be specified using OR, such as `INSERT`, `UPDATE`, `DELETE`, or `TRUNCATE`.
         events: Vec<TriggerEvent>,
         /// The table on which the trigger is to be created.
@@ -3980,6 +3989,8 @@ pub enum Statement {
         condition: Option<Expr>,
         /// Execute logic block
         exec_body: Option<TriggerExecBody>,
+        /// For MSSQL and dialects where statements are preceded by `AS`
+        statements_as: bool,
         /// For SQL dialects with statement(s) for a body
         statements: Option<ConditionalStatements>,
         /// The characteristic of the trigger, which include whether the trigger is `DEFERRABLE`, `INITIALLY DEFERRED`, or `INITIALLY IMMEDIATE`,
@@ -4944,6 +4955,7 @@ impl fmt::Display for Statement {
                 or_replace,
                 is_constraint,
                 name,
+                period_before_table,
                 period,
                 events,
                 table_name,
@@ -4953,6 +4965,7 @@ impl fmt::Display for Statement {
                 condition,
                 include_each,
                 exec_body,
+                statements_as,
                 statements,
                 characteristics,
             } => {
@@ -4964,7 +4977,7 @@ impl fmt::Display for Statement {
                     is_constraint = if *is_constraint { "CONSTRAINT " } else { "" },
                 )?;
 
-                if exec_body.is_some() {
+                if *period_before_table {
                     write!(f, "{period}")?;
                     if !events.is_empty() {
                         write!(f, " {}", display_separated(events, " OR "))?;
@@ -5002,7 +5015,10 @@ impl fmt::Display for Statement {
                     write!(f, " EXECUTE {exec_body}")?;
                 }
                 if let Some(statements) = statements {
-                    write!(f, " AS {statements}")?;
+                    if *statements_as {
+                        write!(f, " AS")?;
+                    }
+                    write!(f, " {statements}")?;
                 }
                 Ok(())
             }

src/dialect/mssql.rs

@@ -257,6 +257,7 @@ impl MsSqlDialect {
             is_constraint: false,
             name,
             period,
+            period_before_table: false,
             events,
             table_name,
             referenced_table_name: None,
@@ -265,6 +266,7 @@ impl MsSqlDialect {
             include_each: false,
             condition: None,
             exec_body: None,
+            statements_as: true,
             statements,
             characteristics: None,
         })

src/parser/mod.rs

@@ -5593,25 +5593,31 @@ impl<'a> Parser<'a> {
             .then(|| self.parse_expr())
             .transpose()?;
 
-        self.expect_keyword_is(Keyword::EXECUTE)?;
-
-        let exec_body = self.parse_trigger_exec_body()?;
+        let mut exec_body = None;
+        let mut statements = None;
+        if self.parse_keyword(Keyword::EXECUTE) {
+            exec_body = Some(self.parse_trigger_exec_body()?);
+        } else {
+            statements = Some(self.parse_conditional_statements(&[Keyword::END])?);
+        }
 
         Ok(Statement::CreateTrigger {
             or_alter,
             or_replace,
             is_constraint,
             name,
             period,
+            period_before_table: true,
             events,
             table_name,
             referenced_table_name,
             referencing,
             trigger_object,
             include_each,
             condition,
-            exec_body: Some(exec_body),
-            statements: None,
+            exec_body,
+            statements_as: false,
+            statements,
             characteristics,
         })
     }
@@ -6537,7 +6543,7 @@ impl<'a> Parser<'a> {
 
         let args = if self.consume_token(&Token::LParen) {
             if self.consume_token(&Token::RParen) {
-                None
+                Some(vec![])
             } else {
                 let args = self.parse_comma_separated(Parser::parse_function_arg)?;
                 self.expect_token(&Token::RParen)?;

tests/sqlparser_mssql.rs

@@ -2376,6 +2376,7 @@ fn parse_create_trigger() {
             is_constraint: false,
             name: ObjectName::from(vec![Ident::new("reminder1")]),
             period: TriggerPeriod::After,
+            period_before_table: false,
             events: vec![TriggerEvent::Insert, TriggerEvent::Update(vec![]),],
             table_name: ObjectName::from(vec![Ident::new("Sales"), Ident::new("Customer")]),
             referenced_table_name: None,
@@ -2384,6 +2385,7 @@ fn parse_create_trigger() {
             include_each: false,
             condition: None,
             exec_body: None,
+            statements_as: true,
             statements: Some(ConditionalStatements::Sequence {
                 statements: vec![Statement::RaisError {
                     message: Box::new(Expr::Value(

tests/sqlparser_mysql.rs

@@ -3914,11 +3914,8 @@ fn parse_looks_like_single_line_comment() {
 
 #[test]
 fn parse_create_trigger() {
-    let sql_create_trigger = r#"
-        CREATE TRIGGER emp_stamp BEFORE INSERT ON emp
-            FOR EACH ROW EXECUTE FUNCTION emp_stamp();
-    "#;
-    let create_stmt = mysql().one_statement_parses_to(sql_create_trigger, "");
+    let sql_create_trigger = r#"CREATE TRIGGER emp_stamp BEFORE INSERT ON emp FOR EACH ROW EXECUTE FUNCTION emp_stamp()"#;
+    let create_stmt = mysql().verified_stmt(sql_create_trigger);
     assert_eq!(
         create_stmt,
         Statement::CreateTrigger {
@@ -3927,6 +3924,7 @@ fn parse_create_trigger() {
             is_constraint: false,
             name: ObjectName::from(vec![Ident::new("emp_stamp")]),
             period: TriggerPeriod::Before,
+            period_before_table: true,
             events: vec![TriggerEvent::Insert],
             table_name: ObjectName::from(vec![Ident::new("emp")]),
             referenced_table_name: None,
@@ -3938,15 +3936,22 @@ fn parse_create_trigger() {
                 exec_type: TriggerExecBodyType::Function,
                 func_desc: FunctionDesc {
                     name: ObjectName::from(vec![Ident::new("emp_stamp")]),
-                    args: None,
+                    args: Some(vec![]),
                 }
             }),
+            statements_as: false,
             statements: None,
             characteristics: None,
         }
     );
 }
 
+#[test]
+fn parse_create_trigger_compound_statement() {
+    mysql_and_generic().verified_stmt("CREATE TRIGGER mytrigger BEFORE INSERT ON mytable FOR EACH ROW BEGIN SET NEW.a = 1; SET NEW.b = 2; END");
+    mysql_and_generic().verified_stmt("CREATE TRIGGER tr AFTER INSERT ON t1 FOR EACH ROW BEGIN INSERT INTO t2 VALUES (NEW.id); END");
+}
+
 #[test]
 fn parse_drop_trigger() {
     let sql_drop_trigger = "DROP TRIGGER emp_stamp;";

tests/sqlparser_postgres.rs

@@ -5552,6 +5552,7 @@ fn parse_create_simple_before_insert_trigger() {
         is_constraint: false,
         name: ObjectName::from(vec![Ident::new("check_insert")]),
         period: TriggerPeriod::Before,
+        period_before_table: true,
         events: vec![TriggerEvent::Insert],
         table_name: ObjectName::from(vec![Ident::new("accounts")]),
         referenced_table_name: None,
@@ -5566,6 +5567,7 @@ fn parse_create_simple_before_insert_trigger() {
                 args: None,
             },
         }),
+        statements_as: false,
         statements: None,
         characteristics: None,
     };
@@ -5582,6 +5584,7 @@ fn parse_create_after_update_trigger_with_condition() {
         is_constraint: false,
         name: ObjectName::from(vec![Ident::new("check_update")]),
         period: TriggerPeriod::After,
+        period_before_table: true,
         events: vec![TriggerEvent::Update(vec![])],
         table_name: ObjectName::from(vec![Ident::new("accounts")]),
         referenced_table_name: None,
@@ -5603,6 +5606,7 @@ fn parse_create_after_update_trigger_with_condition() {
                 args: None,
             },
         }),
+        statements_as: false,
         statements: None,
         characteristics: None,
     };
@@ -5619,6 +5623,7 @@ fn parse_create_instead_of_delete_trigger() {
         is_constraint: false,
         name: ObjectName::from(vec![Ident::new("check_delete")]),
         period: TriggerPeriod::InsteadOf,
+        period_before_table: true,
         events: vec![TriggerEvent::Delete],
         table_name: ObjectName::from(vec![Ident::new("accounts")]),
         referenced_table_name: None,
@@ -5633,6 +5638,7 @@ fn parse_create_instead_of_delete_trigger() {
                 args: None,
             },
         }),
+        statements_as: false,
         statements: None,
         characteristics: None,
     };
@@ -5649,6 +5655,7 @@ fn parse_create_trigger_with_multiple_events_and_deferrable() {
         is_constraint: true,
         name: ObjectName::from(vec![Ident::new("check_multiple_events")]),
         period: TriggerPeriod::Before,
+        period_before_table: true,
         events: vec![
             TriggerEvent::Insert,
             TriggerEvent::Update(vec![]),
@@ -5667,6 +5674,7 @@ fn parse_create_trigger_with_multiple_events_and_deferrable() {
                 args: None,
             },
         }),
+        statements_as: false,
         statements: None,
         characteristics: Some(ConstraintCharacteristics {
             deferrable: Some(true),
@@ -5687,6 +5695,7 @@ fn parse_create_trigger_with_referencing() {
         is_constraint: false,
         name: ObjectName::from(vec![Ident::new("check_referencing")]),
         period: TriggerPeriod::Before,
+        period_before_table: true,
         events: vec![TriggerEvent::Insert],
         table_name: ObjectName::from(vec![Ident::new("accounts")]),
         referenced_table_name: None,
@@ -5712,6 +5721,7 @@ fn parse_create_trigger_with_referencing() {
                 args: None,
             },
         }),
+        statements_as: false,
         statements: None,
         characteristics: None,
     };
@@ -5994,6 +6004,7 @@ fn parse_trigger_related_functions() {
             is_constraint: false,
             name: ObjectName::from(vec![Ident::new("emp_stamp")]),
             period: TriggerPeriod::Before,
+            period_before_table: true,
             events: vec![TriggerEvent::Insert, TriggerEvent::Update(vec![])],
             table_name: ObjectName::from(vec![Ident::new("emp")]),
             referenced_table_name: None,
@@ -6005,9 +6016,10 @@ fn parse_trigger_related_functions() {
                 exec_type: TriggerExecBodyType::Function,
                 func_desc: FunctionDesc {
                     name: ObjectName::from(vec![Ident::new("emp_stamp")]),
-                    args: None,
+                    args: Some(vec![]),
                 }
             }),
+            statements_as: false,
             statements: None,
             characteristics: None
         }