fix: find tables in SET values instead of throwing (#2873)

TablesNamesFinder threw UnsupportedOperationException for every SET
statement except SQL Server ON/OFF options. A MySQL trigger whose body
is or contains SET, such as FOR EACH ROW SET NEW.a = ..., failed the
same way, although its table is known.

The finder now visits the value expressions of each assignment, so a
subquery in a SET value reports its tables and other SET statements
report none.

Signed-off-by: minleejae <mmj9808@gmail.com>

Author: minleejae

src/main/java/net/sf/jsqlparser/util/TablesNamesFinder.java

@@ -1950,8 +1950,13 @@ public void visit(Execute execute) {
 
     @Override
     public <S> Void visit(SetStatement setStatement, S context) {
-        if (setStatement.getOnOffOptions() == null) {
-            throwUnsupported(setStatement);
+        for (int i = 0; i < setStatement.getCount(); i++) {
+            List<Expression> expressions = setStatement.getExpressions(i);
+            if (expressions != null) {
+                for (Expression expression : expressions) {
+                    expression.accept(this, context);
+                }
+            }
         }
         return null;
     }

src/test/java/net/sf/jsqlparser/util/TablesNamesFinderTest.java

@@ -392,6 +392,27 @@ public void testAlterSequenceHasNoTableReferences() throws JSQLParserException {
         assertThat(tablesNamesFinder.getTables(stmt)).isEmpty();
     }
 
+    @Test
+    public void testSetStatementFindsTablesInValues() throws JSQLParserException {
+        assertThat(TablesNamesFinder
+                .findTables("SET @a = (SELECT MAX(id) FROM MY_TABLE1), @b = 2"))
+                .containsExactlyInAnyOrder("MY_TABLE1");
+        assertThat(TablesNamesFinder.findTables("SET search_path TO s1")).isEmpty();
+    }
+
+    @Test
+    public void testMySqlTriggerWithSetBody() throws JSQLParserException {
+        String sqlStr = "CREATE TRIGGER trg BEFORE INSERT ON MY_TABLE1 FOR EACH ROW "
+                + "SET NEW.a = (SELECT MAX(id) FROM MY_TABLE2)";
+        assertThat(TablesNamesFinder.findTables(sqlStr)).containsExactlyInAnyOrder("MY_TABLE1",
+                "MY_TABLE2");
+
+        sqlStr = "CREATE TRIGGER trg BEFORE UPDATE ON MY_TABLE1 FOR EACH ROW "
+                + "BEGIN SET NEW.updated_at = NOW(); INSERT INTO MY_TABLE2 VALUES (NEW.id); END";
+        assertThat(TablesNamesFinder.findTables(sqlStr)).containsExactlyInAnyOrder("MY_TABLE1",
+                "MY_TABLE2");
+    }
+
     @Test
     public void testCreateSynonym_throwsException() throws JSQLParserException {
         String sql = "CREATE SYNONYM foo FOR bar";