bugfix for INTERVAL

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -458,6 +458,11 @@ public class SQLExprParser extends SQLParser {
                         sqlExpr = new SQLNumberExpr(lexer.decimalValue());
                         lexer.nextToken();
                         break;
+                    case IDENTIFIER: // 当+号后面为字段的情况
+                        sqlExpr = new SQLIdentifierExpr(lexer.stringVal());
+                        sqlExpr = new SQLUnaryExpr(SQLUnaryOperator.Plus, sqlExpr);
+                        lexer.nextToken();
+                        break;
                     case LPAREN:
                         lexer.nextToken();
                         sqlExpr = expr();

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

@@ -621,6 +621,29 @@ public class DateAndTimeFunctionsTest extends TestCase {
 
         Assert.assertEquals("SELECT YEARWEEK('1987-01-01');", text);
     }
+    
+    
+    public void test_54() throws Exception {
+        String sql = "SELECT t.c1, DATE_ADD('2008-01-02', INTERVAL +t.c1 DAY) from t";
+
+        SQLStatementParser parser = new MySqlStatementParser(sql);
+        List<SQLStatement> stmtList = parser.parseStatementList();
+
+        String text = output(stmtList);
+
+        Assert.assertEquals("SELECT t.c1, DATE_ADD('2008-01-02', INTERVAL +t.c1 DAY)\nFROM t;", text);
+    }
+    
+    public void test_55() throws Exception {
+        String sql = "SELECT t.c1, DATE_ADD('2008-01-02', INTERVAL -t.c1 DAY) from t";
+
+        SQLStatementParser parser = new MySqlStatementParser(sql);
+        List<SQLStatement> stmtList = parser.parseStatementList();
+
+        String text = output(stmtList);
+
+        Assert.assertEquals("SELECT t.c1, DATE_ADD('2008-01-02', INTERVAL -t.c1 DAY)\nFROM t;", text);
+    }
 
     private String output(List<SQLStatement> stmtList) {
         StringBuilder out = new StringBuilder();