Issue 391 expression for interval.

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

@@ -314,6 +314,7 @@ public void visit(ExtractExpression expr) {
 
     @Override
     public void visit(IntervalExpression expr) {
+        expr.getParameter().accept(this);
     }
 
     @Override

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

@@ -27,14 +27,14 @@
  */
 public class IntervalExpression implements Expression {
 
-    private String parameter = null;
+    private Expression parameter = null;
     private String intervalType = null;
 
-    public String getParameter() {
+    public Expression getParameter() {
         return parameter;
     }
 
-    public void setParameter(String parameter) {
+    public void setParameter(Expression parameter) {
         this.parameter = parameter;
     }
 

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

@@ -421,6 +421,7 @@ protected void init() {
 
     @Override
     public void visit(IntervalExpression iexpr) {
+        iexpr.getParameter().accept(this);
     }
 
     @Override

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

@@ -522,7 +522,11 @@ public void visit(MultiExpressionList multiExprList) {
 
     @Override
     public void visit(IntervalExpression iexpr) {
-        buffer.append(iexpr.toString());
+        buffer.append("INTERVAL ");
+        iexpr.getParameter().accept(this);
+        if(iexpr.getIntervalType() != null) {
+            buffer.append(" ").append(iexpr.getIntervalType());
+        }
     }
 
     @Override

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -2272,12 +2272,13 @@ JsonExpression JsonExpression() : {
 
 IntervalExpression IntervalExpression() : {
     IntervalExpression interval = new IntervalExpression();
+    Expression item;
     Token token;
     boolean signed = false;
 }
 {
-    <K_INTERVAL> ["-" {signed=true;}] (token=<S_LONG> | token=<S_DOUBLE> | token=<S_CHAR_LITERAL>) 
-    { interval.setParameter((signed?"-":"") + token.image); }
+    <K_INTERVAL> (item = PrimaryExpression())
+    { interval.setParameter(item); }
     [ LOOKAHEAD(2) token = <S_IDENTIFIER> { interval.setIntervalType(token.image); } ]
     {
         return interval;
@@ -3095,20 +3096,30 @@ List<ConstraintState> AlterExpressionConstraintState():
 }
 {
     (
-        (          <K_DEFERRABLE> {retval.add(new DeferrableConstraint(false));}
+        (
+          <K_DEFERRABLE> {retval.add(new DeferrableConstraint(false));}
         )
         |
         (
-          <K_NOT> <K_DEFERRABLE> {retval.add(new DeferrableConstraint(true));}        ) 
+          <K_NOT> <K_DEFERRABLE> {retval.add(new DeferrableConstraint(true));}
+        ) 
+        |
+        (
+          <K_VALIDATE> {retval.add(new ValidateConstraint(false));}
+        )
+        |
+        (
+          <K_NOVALIDATE> {retval.add(new ValidateConstraint(true));}
+        )
         |
-        (          <K_VALIDATE> {retval.add(new ValidateConstraint(false));}
-        )        |
-        (          <K_NOVALIDATE> {retval.add(new ValidateConstraint(true));}
-        )        |
-        (          <K_ENABLE> {retval.add(new EnableConstraint(false));}
-        )        |
-        (          <K_DISABLE> {retval.add(new EnableConstraint(true));}
-        )    )*
+        (
+          <K_ENABLE> {retval.add(new EnableConstraint(false));}
+        )
+        |
+        (
+          <K_DISABLE> {retval.add(new EnableConstraint(true));}
+        )
+    )*
     {
         return retval;
     }

src/test/java/net/sf/jsqlparser/test/select/SelectTest.java

@@ -1852,7 +1852,7 @@ public void testInterval2() throws JSQLParserException {
         assertTrue(sub.getRightExpression() instanceof IntervalExpression);
         IntervalExpression iexpr = (IntervalExpression) sub.getRightExpression();
 
-        assertEquals("'45 MINUTE'", iexpr.getParameter());
+        assertEquals("'45 MINUTE'", iexpr.getParameter().toString());
     }
 
     public void testInterval3() throws JSQLParserException {