chore: tweak txn syntax (#14960)

Author: SkyFan2002

src/query/ast/src/parser/statement.rs

@@ -1986,7 +1986,7 @@ pub fn statement_body(i: Input) -> IResult<Statement> {
         },
     );
 
-    let begin = value(Statement::Begin, rule! { BEGIN });
+    let begin = value(Statement::Begin, rule! { BEGIN ~ (TRANSACTION)? });
     let commit = value(Statement::Commit, rule! { COMMIT });
     let abort = value(Statement::Abort, rule! { ABORT | ROLLBACK });
 

src/query/ast/src/parser/token.rs

@@ -1213,6 +1213,8 @@ pub enum TokenKind {
     UNTIL,
     #[token("BEGIN", ignore(ascii_case))]
     BEGIN,
+    #[token("TRANSACTION", ignore(ascii_case))]
+    TRANSACTION,
     #[token("COMMIT", ignore(ascii_case))]
     COMMIT,
     #[token("ABORT", ignore(ascii_case))]
@@ -1541,6 +1543,7 @@ impl TokenKind {
             // | TokenKind::TABLESAMPLE
             | TokenKind::THEN
             | TokenKind::TRAILING
+            | TokenKind::TRANSACTION
             | TokenKind::TRUE
             // | TokenKind::UNIQUE
             //| TokenKind::USER

tests/sqllogictests/suites/base/14_transaction/14_0003_merge_into.test

@@ -69,5 +69,80 @@ SELECT employee_id, salary FROM salaries order by employee_id;
 4   55000.00
 
 
+statement ok
+drop database test_txn_merge_into;
+
+
+statement ok
+create or replace database test_txn_merge_into;
+
+statement ok
+use test_txn_merge_into;
+
+statement ok
+set enable_experimental_merge_into = 1;
+
+statement ok
+CREATE TABLE employees (
+    employee_id INT,
+    employee_name VARCHAR(255),
+    department VARCHAR(255)
+);
+
+statement ok
+CREATE TABLE salaries (
+    employee_id INT,
+    salary DECIMAL(10, 2)
+);
+
+statement ok
+BEGIN TRANSACTION;
+
+statement ok
+INSERT INTO employees VALUES
+    (1, 'Alice', 'HR'),
+    (2, 'Bob', 'IT'),
+    (3, 'Charlie', 'Finance'),
+    (4, 'David', 'HR');
+
+statement ok
+INSERT INTO salaries VALUES
+    (1, 50000.00),
+    (2, 60000.00);
+
+statement ok
+MERGE INTO salaries
+    USING (SELECT * FROM employees) AS employees
+    ON salaries.employee_id = employees.employee_id
+    WHEN MATCHED AND employees.department = 'HR' THEN
+        UPDATE SET
+            salaries.salary = salaries.salary + 1000.00
+    WHEN MATCHED THEN
+        UPDATE SET
+            salaries.salary = salaries.salary + 500.00
+    WHEN NOT MATCHED THEN
+        INSERT (employee_id, salary)
+            VALUES (employees.employee_id, 55000.00);
+
+query IF
+SELECT employee_id, salary FROM salaries order by employee_id;
+----
+1   51000.00
+2   60500.00
+3   55000.00
+4   55000.00
+
+statement ok
+COMMIT;
+
+query IF
+SELECT employee_id, salary FROM salaries order by employee_id;
+----
+1   51000.00
+2   60500.00
+3   55000.00
+4   55000.00
+
+
 statement ok
 drop database test_txn_merge_into;