Fix: mysql comment with = (#1936)

* Fix: mysql comment with `=`

* Fix: mysql comment with `=`

Author: jxnu-liguobin

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

@@ -442,8 +442,11 @@ public String toString() {
             // Oracle Multi Column Drop
             b.append("DROP (").append(PlainSelect.getStringList(pkColumns)).append(')');
         } else {
-            b.append(operation).append(" ");
-
+            if (operation == AlterOperation.COMMENT_WITH_EQUAL_SIGN) {
+                b.append("COMMENT =").append(" ");
+            } else {
+                b.append(operation).append(" ");
+            }
             if (commentText != null) {
                 if (columnName != null) {
                     b.append(columnName).append(" COMMENT ");

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

@@ -10,7 +10,7 @@
 package net.sf.jsqlparser.statement.alter;
 
 public enum AlterOperation {
-    ADD, ALTER, DROP, DROP_PRIMARY_KEY, DROP_UNIQUE, DROP_FOREIGN_KEY, MODIFY, CHANGE, ALGORITHM, RENAME, RENAME_TABLE, RENAME_INDEX, RENAME_KEY, RENAME_CONSTRAINT, COMMENT, UNSPECIFIC;
+    ADD, ALTER, DROP, DROP_PRIMARY_KEY, DROP_UNIQUE, DROP_FOREIGN_KEY, MODIFY, CHANGE, ALGORITHM, RENAME, RENAME_TABLE, RENAME_INDEX, RENAME_KEY, RENAME_CONSTRAINT, COMMENT, COMMENT_WITH_EQUAL_SIGN, UNSPECIFIC;
 
     public static AlterOperation from(String operation) {
         return Enum.valueOf(AlterOperation.class, operation.toUpperCase());

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

@@ -6500,6 +6500,7 @@ AlterExpression AlterExpression():
       )
       |
       (<K_COMMENT> {alterExp.setOperation(AlterOperation.COMMENT);}
+          ["=" {alterExp.setOperation(AlterOperation.COMMENT_WITH_EQUAL_SIGN);} ]
           tk=<S_CHAR_LITERAL> { alterExp.setCommentText(tk.image); }
       )
       |

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

@@ -896,6 +896,12 @@ public void testAlterTableDropColumnIfExists() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("ALTER TABLE test DROP COLUMN IF EXISTS name");
     }
 
+    @Test
+    public void testAlterTableCommentIssue1935() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("ALTER TABLE table_name COMMENT = 'New table comment'");
+        assertSqlCanBeParsedAndDeparsed("ALTER TABLE table_name COMMENT 'New table comment'");
+    }
+
     @Test
     public void testAlterTableDropMultipleColumnsIfExists() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed(