improved mysql ddl support, fix #4039

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -8005,6 +8005,16 @@ public class MySqlStatementParser extends SQLStatementParser {
 
         SQLCreateDatabaseStatement stmt = new SQLCreateDatabaseStatement(dbType);
 
+        if (lexer.token() == Token.HINT) {
+            List<SQLCommentHint> hints = this.exprParser.parseHints();
+            if (hints.size() == 1) {
+                String text = hints.get(0).getText();
+                if (text.endsWith(" IF NOT EXISTS") && text.charAt(0) == '!') {
+                    stmt.setIfNotExists(true);
+                }
+            }
+        }
+
         if (lexer.token() == Token.IF) {
             lexer.nextToken();
             accept(Token.NOT);

src/test/java/com/alibaba/druid/bvt/sql/mysql/visitor/MySqlResourceTest.java

@@ -50,6 +50,10 @@ public class MySqlResourceTest extends TestCase {
         exec_test("bvt/parser/mysql-14.txt");
     }
 
+    public void test_16() throws Exception {
+        exec_test("bvt/parser/mysql-16.txt");
+    }
+
     public void exec_test(String resource) throws Exception {
 //        System.out.println(resource);
         InputStream is = null;
@@ -64,12 +68,12 @@ public class MySqlResourceTest extends TestCase {
 
         MySqlStatementParser parser = new MySqlStatementParser(sql);
         List<SQLStatement> statementList = parser.parseStatementList();
-        SQLStatement statemen = statementList.get(0);
+        SQLStatement stmt = statementList.get(0);
 
-        Assert.assertEquals(1, statementList.size());
+        assertEquals(1, statementList.size());
 
         MySqlSchemaStatVisitor visitor = new MySqlSchemaStatVisitor();
-        statemen.accept(visitor);
+        stmt.accept(visitor);
 
 //        System.out.println(sql);
 //        System.out.println("Tables : " + visitor.getTables());
@@ -77,6 +81,10 @@ public class MySqlResourceTest extends TestCase {
 //
 //        System.out.println();
 //        System.out.println();
+
+        if (expect != null && !expect.isEmpty()) {
+            assertEquals(expect, stmt.toString());
+        }
     }
 
     void mergValidate(String sql, String expect) {

src/test/resources/bvt/parser/mysql-16.txt

@@ -0,0 +1,3 @@
+CREATE DATABASE /*!32312 IF NOT EXISTS*/ `druidtestdb` /*!40100 DEFAULT CHARACTER SET utf8 COLLATE utf8_bin */;
+---------------------------
+CREATE DATABASE IF NOT EXISTS `druidtestdb`;