fixes #588

Author: wumpz

src/main/java/net/sf/jsqlparser/expression/operators/relational/IsNullExpression.java

@@ -29,6 +29,7 @@ public class IsNullExpression extends ASTNodeAccessImpl implements Expression {
 
     private Expression leftExpression;
     private boolean not = false;
+    private boolean useIsNull = false;
 
     public Expression getLeftExpression() {
         return leftExpression;
@@ -46,13 +47,25 @@ public void setNot(boolean b) {
         not = b;
     }
 
+    public boolean isUseIsNull() {
+        return useIsNull;
+    }
+
+    public void setUseIsNull(boolean useIsNull) {
+        this.useIsNull = useIsNull;
+    }
+
     @Override
     public void accept(ExpressionVisitor expressionVisitor) {
         expressionVisitor.visit(this);
     }
 
     @Override
     public String toString() {
-        return leftExpression + " IS " + (not ? "NOT " : "") + "NULL";
+        if (isUseIsNull()) {
+            return leftExpression + (not ? " NOT" : "") + " ISNULL";
+        } else {
+            return leftExpression + " IS " + (not ? "NOT " : "") + "NULL";
+        }
     }
 }

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

@@ -262,10 +262,18 @@ public void visit(SignedExpression signedExpression) {
     @Override
     public void visit(IsNullExpression isNullExpression) {
         isNullExpression.getLeftExpression().accept(this);
-        if (isNullExpression.isNot()) {
-            buffer.append(" IS NOT NULL");
+        if (isNullExpression.isUseIsNull()) {
+            if (isNullExpression.isNot()) {
+                buffer.append(" NOT ISNULL");
+            } else {
+                buffer.append(" ISNULL");
+            }
         } else {
-            buffer.append(" IS NULL");
+            if (isNullExpression.isNot()) {
+                buffer.append(" IS NOT NULL");
+            } else {
+                buffer.append(" IS NULL");
+            }
         }
     }
 
@@ -727,7 +735,7 @@ public void visit(KeepExpression aexpr) {
     public void visit(MySQLGroupConcat groupConcat) {
         buffer.append(groupConcat.toString());
     }
-    
+
     @Override
     public void visit(ValueListExpression valueList) {
         buffer.append(valueList.toString());

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

@@ -203,6 +203,7 @@ TOKEN: /* SQL Keywords. prefixed with K_ to avoid name clashes */
 |   <K_INTERVAL:"INTERVAL">
 |   <K_INTO:"INTO">
 |   <K_IS:"IS">
+|   <K_ISNULL:"ISNULL">
 |   <K_JOIN:"JOIN">
 |   <K_KEEP:"KEEP">
 |   <K_KEY:"KEY">
@@ -2169,9 +2170,11 @@ Expression IsNullExpression():
 }
 {
     (
-    <K_NOT> { result.setNot(true); } leftExpression=SimpleExpression() <K_IS> <K_NULL>
+    <K_NOT> { result.setNot(true); } leftExpression=SimpleExpression() 
+        ( <K_ISNULL> { result.setUseIsNull(true); } | <K_IS> <K_NULL> )
     |
-    leftExpression=SimpleExpression() <K_IS> [<K_NOT> { result.setNot(true); } ] <K_NULL>
+    leftExpression=SimpleExpression() 
+        (<K_ISNULL> { result.setUseIsNull(true); } | <K_IS> [<K_NOT> { result.setNot(true); } ] <K_NULL> )
     )
 
     {

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

@@ -2764,4 +2764,8 @@ public void testIssue584MySQLValueListExpression() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT a, b FROM T WHERE (T.a, T.b) = (c, d)");
         assertSqlCanBeParsedAndDeparsed("SELECT a FROM T WHERE (T.a) = (SELECT b FROM T, c, d)");
     }
+    
+    public void testIssue588NotNull() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM mytable WHERE col1 ISNULL");
+    }
 }