huaxingao commented on a change in pull request #29324:
URL: https://github.com/apache/spark/pull/29324#discussion_r464825759



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala
##########
@@ -184,15 +189,62 @@ abstract class JdbcDialect extends Serializable {
   /**
    * Rename an existing table.
    *
-   * TODO (SPARK-32382): Override this method in the dialects that don't 
support such syntax.
-   *
    * @param oldTable The existing table.
    * @param newTable New name of the table.
    * @return The SQL statement to use for renaming the table.
    */
   def renameTable(oldTable: String, newTable: String): String = {
     s"ALTER TABLE $oldTable RENAME TO $newTable"
   }
+
+  /**
+   * Alter an existing table.
+   * TODO (SPARK-32523): Override this method in the dialects that have 
different syntax.
+   *
+   * @param tableName The name of the table to be altered.
+   * @param changes Changes to apply to the table.
+   * @return The SQL statements to use for altering the table.
+   */
+  def alterTable(tableName: String, changes: Seq[TableChange]): Array[String] 
= {
+    val updateClause = ArrayBuilder.make[String]
+    for (change <- changes) {
+      change match {
+        case add: AddColumn =>
+          add.fieldNames match {
+            case Array(name) =>

Review comment:
       Does this look OK?
   ```
               case _ =>
                 throw new SQLFeatureNotSupportedException("Nested column is 
not supported.")
   ```




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