Merge pull request #1037 from wenshao/master

mysql sql parser support 'create database if not exists'

src/main/java/com/alibaba/druid/sql/ast/statement/SQLCreateDatabaseStatement.java

@@ -30,6 +30,8 @@ public class SQLCreateDatabaseStatement extends SQLStatementImpl {
     private String               collate;
 
     private List<SQLCommentHint> hints;
+    
+    protected boolean            ifNotExists = false;
 
     public SQLCreateDatabaseStatement(){
     }
@@ -77,5 +79,13 @@ public class SQLCreateDatabaseStatement extends SQLStatementImpl {
     public void setHints(List<SQLCommentHint> hints) {
         this.hints = hints;
     }
+    
+    public boolean isIfNotExists() {
+        return ifNotExists;
+    }
+    
+    public void setIfNotExists(boolean ifNotExists) {
+        this.ifNotExists = ifNotExists;
+    }
 
 }

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

@@ -2688,6 +2688,14 @@ public class MySqlStatementParser extends SQLStatementParser {
         accept(Token.DATABASE);
 
         SQLCreateDatabaseStatement stmt = new SQLCreateDatabaseStatement(JdbcConstants.MYSQL);
+        
+        if (lexer.token() == Token.IF) {
+            lexer.nextToken();
+            accept(Token.NOT);
+            accept(Token.EXISTS);
+            stmt.setIfNotExists(true);
+        }
+        
         stmt.setName(this.exprParser.name());
 
         if (lexer.token() == Token.DEFAULT) {

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -1601,6 +1601,9 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Printab
     @Override
     public boolean visit(SQLCreateDatabaseStatement x) {
         print0(ucase ? "CREATE DATABASE " : "create database ");
+        if (x.isIfNotExists()) {
+            print0(ucase ? "IF NOT EXISTS " : "if not exists ");    
+        }
         x.getName().accept(this);
         return false;
     }

src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlCreateDatabaseTest.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 1999-2101 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.druid.bvt.sql.mysql;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.alibaba.druid.sql.MysqlTest;
+import com.alibaba.druid.sql.SQLUtils;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
+import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlSchemaStatVisitor;
+
+public class MySqlCreateDatabaseTest extends MysqlTest {
+
+    @Test
+    public void test_one() throws Exception {
+        String sql = "create database if not exists a";
+
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatement();
+
+        MySqlSchemaStatVisitor visitor = new MySqlSchemaStatVisitor();
+        stmt.accept(visitor);
+
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("CREATE DATABASE IF NOT EXISTS a", output);
+    }
+}