fix: expose IntervalExpression attributes and use DeParser

Author: manticore-projects

src/main/java/net/sf/jsqlparser/expression/IntervalExpression.java

@@ -9,9 +9,10 @@
  */
 package net.sf.jsqlparser.expression;
 
-import java.util.Objects;
 import net.sf.jsqlparser.parser.ASTNodeAccessImpl;
 
+import java.util.Objects;
+
 public class IntervalExpression extends ASTNodeAccessImpl implements Expression {
 
     private String parameter = null;
@@ -27,6 +28,10 @@ public IntervalExpression(boolean intervalKeyword) {
         this.intervalKeyword = intervalKeyword;
     }
 
+    public boolean isUsingIntervalKeyword() {
+        return intervalKeyword;
+    }
+
     public String getParameter() {
         return parameter;
     }

src/main/java/net/sf/jsqlparser/util/deparser/ExpressionDeParser.java

@@ -816,8 +816,18 @@ public void visit(ExtractExpression eexpr) {
     }
 
     @Override
-    public void visit(IntervalExpression iexpr) {
-        buffer.append(iexpr.toString());
+    public void visit(IntervalExpression intervalExpression) {
+        if (intervalExpression.isUsingIntervalKeyword()) {
+            buffer.append("INTERVAL ");
+        }
+        if (intervalExpression.getExpression()!=null) {
+            intervalExpression.getExpression().accept(this);
+        } else {
+            buffer.append(intervalExpression.getParameter());
+        }
+        if (intervalExpression.getIntervalType()!=null) {
+            buffer.append(" ").append(intervalExpression.getIntervalType());
+        }
     }
 
     @Override