feat: syntax sugar

Signed-off-by: Andreas Reichel <andreas@manticore-projects.com>

Author: manticore-projects

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

@@ -29,7 +29,7 @@ public IsNullExpression(Expression leftExpression) {
 
     public IsNullExpression(String columnName, boolean not) {
         this.leftExpression = new Column(columnName);
-        this.not = useNotNull;
+        this.not = not;
     }
 
     public Expression getLeftExpression() {

src/test/java/net/sf/jsqlparser/expression/ArrayExpressionTest.java

@@ -0,0 +1,24 @@
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.schema.Column;
+import net.sf.jsqlparser.statement.select.PlainSelect;
+import net.sf.jsqlparser.statement.select.SelectItem;
+import net.sf.jsqlparser.test.TestUtils;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ArrayExpressionTest {
+
+    @Test
+    void testColumnArrayExpression() throws JSQLParserException {
+        String sqlStr = "SELECT a[2+1] AS a";
+        PlainSelect select = (PlainSelect) TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+        SelectItem<?> selectItem = select.getSelectItem(0);
+
+        Column column = selectItem.getExpression(Column.class);
+        assertInstanceOf(ArrayConstructor.class, column.getArrayConstructor());
+    }
+
+}

src/test/java/net/sf/jsqlparser/expression/operators/relational/IsNullExpressionTest.java

@@ -20,4 +20,10 @@ void testNotNullExpression() throws JSQLParserException {
         String sqlStr = "select * from mytable where 1 notnull";
         TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
     }
+
+    @Test
+    void testStringConstructor() {
+        IsNullExpression isNullExpression= new IsNullExpression("x", true);
+        TestUtils.assertExpressionCanBeDeparsedAs(isNullExpression, "x IS NOT NULL");
+    }
 }