started simple utility function for select statement modification

Author: wumpz

src/main/java/net/sf/jsqlparser/schema/Column.java

@@ -40,6 +40,10 @@ public Column(Table table, String columnName) {
 		this.columnName = columnName;
 	}
 
+	public Column(String columnName) {
+		this(null, columnName);
+	}
+
 	public String getColumnName() {
 		return columnName;
 	}
@@ -61,9 +65,12 @@ public void setTable(Table table) {
 	 */
 	public String getWholeColumnName() {
 
-		String columnWholeName = null;
-		String tableWholeName = table.getWholeTableName();
+		String columnWholeName;
+		String tableWholeName = null;
 
+		if (table != null) {
+			tableWholeName = table.getWholeTableName();
+		}
 		if (tableWholeName != null && tableWholeName.length() != 0) {
 			columnWholeName = tableWholeName + "." + columnName;
 		} else {

src/main/java/net/sf/jsqlparser/statement/select/SelectExpressionItem.java

@@ -32,6 +32,13 @@ public class SelectExpressionItem implements SelectItem {
 	private Expression expression;
 	private Alias alias;
 
+	public SelectExpressionItem() {
+	}
+
+	public SelectExpressionItem(Expression expression) {
+		this.expression = expression;
+	}
+	
 	public Alias getAlias() {
 		return alias;
 	}

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

@@ -0,0 +1,67 @@
+/*
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2014 JSQLParser
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as 
+ * published by the Free Software Foundation, either version 2.1 of the 
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Lesser Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Lesser Public 
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ * #L%
+ */
+package net.sf.jsqlparser.util;
+
+import net.sf.jsqlparser.expression.Expression;
+import net.sf.jsqlparser.statement.select.PlainSelect;
+import net.sf.jsqlparser.statement.select.Select;
+import net.sf.jsqlparser.statement.select.SelectExpressionItem;
+import net.sf.jsqlparser.statement.select.SelectVisitor;
+import net.sf.jsqlparser.statement.select.SetOperationList;
+import net.sf.jsqlparser.statement.select.WithItem;
+
+/**
+ * Utility function for select statements.
+ *
+ * @author toben
+ */
+public final class SelectUtils {
+
+	private SelectUtils() {
+	}
+
+	/**
+	 * Adds an expression to select statements. E.g. a simple column is an expression.
+	 *
+	 * @param select
+	 * @param expr
+	 */
+	public static void addExpression(Select select, final Expression expr) {
+		select.getSelectBody().accept(new SelectVisitor() {
+
+			@Override
+			public void visit(PlainSelect plainSelect) {
+				plainSelect.getSelectItems().add(new SelectExpressionItem(expr));
+			}
+
+			@Override
+			public void visit(SetOperationList setOpList) {
+				throw new UnsupportedOperationException("Not supported yet.");
+			}
+
+			@Override
+			public void visit(WithItem withItem) {
+				throw new UnsupportedOperationException("Not supported yet.");
+			}
+		});
+	}
+}

src/test/java/net/sf/jsqlparser/util/SelectUtilsTest.java

@@ -0,0 +1,49 @@
+package net.sf.jsqlparser.util;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.schema.Column;
+import net.sf.jsqlparser.statement.Statement;
+import net.sf.jsqlparser.statement.select.Select;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ *
+ * @author toben
+ */
+public class SelectUtilsTest {
+
+	public SelectUtilsTest() {
+	}
+
+	@BeforeClass
+	public static void setUpClass() {
+	}
+
+	@AfterClass
+	public static void tearDownClass() {
+	}
+
+	@Before
+	public void setUp() {
+	}
+
+	@After
+	public void tearDown() {
+	}
+
+	/**
+	 * Test of addColumn method, of class SelectUtils.
+	 */
+	@Test
+	public void testAddExpr() throws JSQLParserException {
+		Select select = (Select) CCJSqlParserUtil.parse("select a from mytable");
+		SelectUtils.addExpression(select, new Column("b"));
+		assertEquals("SELECT a, b FROM mytable", select.toString());
+	}
+}