implement feature (#972)

Co-authored-by: Jan Monterrubio <Jan.Monterrubio@Cerner.com>

Author: AnEmortalKid

src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java

@@ -243,7 +243,11 @@ public String toString() {
         b.append(operation).append(" ");
 
         if (columnName != null) {
-            b.append("COLUMN ").append(columnName);
+            b.append("COLUMN ");
+            if (operation == AlterOperation.RENAME) {
+                b.append(columnOldName).append(" TO ");
+            }
+            b.append(columnName);
         } else if (getColDataTypeList() != null) {
             if (operation == AlterOperation.CHANGE) {
                 if (optionalSpecifier != null) {

src/main/java/net/sf/jsqlparser/statement/alter/AlterOperation.java

@@ -10,5 +10,5 @@
 package net.sf.jsqlparser.statement.alter;
 
 public enum AlterOperation {
-    ADD, ALTER, DROP, MODIFY, CHANGE, ALGORITHM;
+    ADD, ALTER, DROP, MODIFY, CHANGE, ALGORITHM, RENAME;
 }

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

@@ -266,6 +266,7 @@ TOKEN: /* SQL Keywords. prefixed with K_ to avoid name clashes */
 |   <K_REFERENCES:"REFERENCES">
 |   <K_REGEXP: "REGEXP">
 |   <K_RLIKE: "RLIKE">
+|   <K_RENAME:"RENAME">
 |   <K_REPLACE:"REPLACE">
 |   <K_RESTRICT: "RESTRICT">
 |   <K_RETURNING: "RETURNING"> 
@@ -4496,6 +4497,15 @@ AlterExpression AlterExpression():
        ["=" { alterExp.setUseEqual(true);} ]
        sk3 = RelObjectName() {alterExp.addParameters(sk3); }
     )
+    |
+    (<K_RENAME> {alterExp.setOperation(AlterOperation.RENAME);}
+      (
+        <K_COLUMN>
+        (tk=<S_IDENTIFIER>    | tk=<S_QUOTED_IDENTIFIER>) { alterExp.setColOldName(tk.image);}
+         (<K_TO>)
+        (tk2=<S_IDENTIFIER>    | tk2=<S_QUOTED_IDENTIFIER>) { alterExp.setColumnName(tk2.image);}
+      )
+    )
     )
 
     {

src/test/java/net/sf/jsqlparser/statement/alter/AlterTest.java

@@ -402,4 +402,16 @@ public void testAlterConstraintWithoutFKSourceColumnsIssue929() throws JSQLParse
     public void testAlterTableAlterColumnDropNotNullIssue918() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("ALTER TABLE \"user_table_t\" ALTER COLUMN name DROP NOT NULL");
     }
+
+    @Test
+    public void testAlterTableRenameColumn() throws JSQLParserException {
+        String sql = "ALTER TABLE \"test_table\" RENAME COLUMN \"test_column\" TO \"test_c\"";
+        assertSqlCanBeParsedAndDeparsed(sql);
+
+        Alter alter= (Alter) CCJSqlParserUtil.parse(sql);
+        AlterExpression expression = alter.getAlterExpressions().get(0);
+        assertEquals(expression.getOperation(), AlterOperation.RENAME);
+        assertEquals(expression.getColOldName(), "\"test_column\"");
+        assertEquals(expression.getColumnName(), "\"test_c\"");
+    }
 }