add collate parsing and tests for order by

Author: ldaIas

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

@@ -5152,9 +5152,11 @@ OrderByElement OrderByElement():
 {
     OrderByElement orderByElement = new OrderByElement();
     Expression columnReference = null;
+    Token collateToken = null;
 }
 {
     columnReference = Expression()
+    [ LOOKAHEAD(<K_COLLATE>) <K_COLLATE> (collateToken=<S_CHAR_LITERAL> | collateToken=<S_QUOTED_IDENTIFIER>) { columnReference = new CollateExpression(columnReference, collateToken.image); } ]
     [ LOOKAHEAD(2) ( <K_ASC> | (<K_DESC> { orderByElement.setAsc(false); } )) { orderByElement.setAscDescPresent(true); }  ]
     [ LOOKAHEAD(2) <K_NULLS>
         [ LOOKAHEAD(2) (

src/test/java/net/sf/jsqlparser/statement/select/OrderByCollateTest.java

@@ -0,0 +1,56 @@
+package net.sf.jsqlparser.statement.select;
+
+import static net.sf.jsqlparser.test.TestUtils.assertSqlCanBeParsedAndDeparsed;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.expression.CollateExpression;
+import org.junit.jupiter.api.Test;
+
+public class OrderByCollateTest {
+
+    @Test
+    public void testOrderByWithCollate() throws JSQLParserException {
+        String sql = "SELECT * FROM a ORDER BY CAST(a.xyz AS TEXT) COLLATE \"und-x-icu\" ASC NULLS FIRST";
+        assertSqlCanBeParsedAndDeparsed(sql);
+    }
+
+    @Test
+    public void testOrderByWithCollateSimple() throws JSQLParserException {
+        String sql = "SELECT * FROM a ORDER BY col COLLATE \"C\" ASC";
+        assertSqlCanBeParsedAndDeparsed(sql);
+    }
+
+    @Test
+    public void testOrderByWithCollateMultiple() throws JSQLParserException {
+        String sql = "SELECT * FROM a ORDER BY col1 COLLATE \"C\" ASC, col2 COLLATE \"POSIX\" DESC";
+        assertSqlCanBeParsedAndDeparsed(sql);
+    }
+
+    @Test
+    public void testOrderByWithCollateAndNulls() throws JSQLParserException {
+        String sql = "SELECT * FROM a ORDER BY col COLLATE \"C\" DESC NULLS LAST";
+        assertSqlCanBeParsedAndDeparsed(sql);
+    }
+
+    @Test
+    public void testOrderByCollateStructure() throws JSQLParserException {
+        String sql = "SELECT * FROM a ORDER BY col COLLATE \"C\" ASC";
+        Select select = (Select) CCJSqlParserUtil.parse(sql);
+        PlainSelect plainSelect = (PlainSelect) select;
+        
+        assertNotNull(plainSelect.getOrderByElements());
+        assertEquals(1, plainSelect.getOrderByElements().size());
+        
+        OrderByElement orderByElement = plainSelect.getOrderByElements().get(0);
+        assertNotNull(orderByElement.getExpression());
+        
+        // The expression should be a CollateExpression
+        if (orderByElement.getExpression() instanceof CollateExpression) {
+            CollateExpression collateExpr = (CollateExpression) orderByElement.getExpression();
+            assertEquals("\"C\"", collateExpr.getCollate());
+        }
+    }
+}