fix: update DELETE samples to match docs (#1072)

[Docs](https://cloud.google.com/spanner/docs/modify-mutation-api#deleting_rows_in_a_table)
list a set of dot points on the multiple ways to perform deletes. The
updated samples now contain examples of these.

samples/crud.js

@@ -134,19 +134,60 @@ async function deleteData(instanceId, databaseId, projectId) {
   const database = instance.database(databaseId);
 
   // Instantiate Spanner table object
-  const singersTable = database.table('Singers');
+  const albumsTable = database.table('Albums');
 
-  // Deletes rows from the Singers table and the Albums table,
-  // because Albums table is defined with ON DELETE CASCADE.
+  // Deletes individual rows from the Albums table.
   try {
-    const keys = [1, 2, 3, 4, 5];
-    await singersTable.deleteRows(keys);
-    console.log('Deleted data.');
+    const keys = [
+      [2, 1],
+      [2, 3],
+    ];
+    await albumsTable.deleteRows(keys);
+    console.log('Deleted individual rows in Albums.');
   } catch (err) {
     console.error('ERROR:', err);
-  } finally {
-    await database.close();
   }
+
+  // Delete a range of rows where the column key is >=3 and <5
+  database.runTransaction(async (err, transaction) => {
+    if (err) {
+      console.error(err);
+      return;
+    }
+    try {
+      const [rowCount] = await transaction.runUpdate({
+        sql: 'DELETE FROM Singers WHERE SingerId >= 3 AND SingerId < 5',
+      });
+      console.log(`${rowCount} records deleted from Singers.`);
+      await transaction.commit();
+    } catch (err) {
+      console.error('ERROR:', err);
+    }
+  });
+
+  // Deletes remaining rows from the Singers table and the Albums table,
+  // because Albums table is defined with ON DELETE CASCADE.
+  database.runTransaction(async (err, transaction) => {
+    if (err) {
+      console.error(err);
+      return;
+    }
+    try {
+      // The WHERE clause is required for DELETE statements to prevent
+      // accidentally deleting all rows in a table.
+      // https://cloud.google.com/spanner/docs/dml-syntax#where_clause
+      const [rowCount] = await transaction.runUpdate({
+        sql: 'DELETE FROM Singers WHERE true',
+      });
+      console.log(`${rowCount} records deleted from Singers.`);
+      await transaction.commit();
+    } catch (err) {
+      console.error('ERROR:', err);
+    } finally {
+      // Close the database when finished.
+      await database.close();
+    }
+  });
   // [END spanner_delete_data]
 }
 

samples/system-test/spanner.test.js

@@ -193,7 +193,9 @@ describe('Spanner', () => {
     let output = execSync(
       `${crudCmd} delete ${INSTANCE_ID} ${DATABASE_ID} ${PROJECT_ID}`
     );
-    assert.match(output, /Deleted data\./);
+    assert.include(output, 'Deleted individual rows in Albums.');
+    assert.include(output, '2 records deleted from Singers.');
+    assert.include(output, '3 records deleted from Singers.');
     output = execSync(
       `${crudCmd} insert ${INSTANCE_ID} ${DATABASE_ID} ${PROJECT_ID}`
     );