Merge pull request #55369 from DerekChia/patch-4

Update replacingmergetree.md

docs/en/engines/table-engines/mergetree-family/replacingmergetree.md

@@ -100,8 +100,43 @@ SELECT * FROM mySecondReplacingMT FINAL;
 The row is deleted when `OPTIMIZE ... FINAL CLEANUP` or `OPTIMIZE ... FINAL` is used, or if the engine setting `clean_deleted_rows` has been set to `Always`.
 
 No matter the operation on the data, the version must be increased. If two inserted rows have the same version number, the last inserted row is the one kept.
+
+Always execute `OPTIMIZE ... FINAL CLEANUP` and `OPTIMIZE ... FINAL` to delete rows with `is_deleted=1` defined, especially when you wish to insert a new row with an older version. Otherwise, the new row with an older version will be replaced and not be persisted.
+
 :::
 
+Example:
+```sql
+-- with ver and is_deleted
+CREATE OR REPLACE TABLE myThirdReplacingMT
+(
+    `key` Int64,
+    `someCol` String,
+    `eventTime` DateTime,
+    `is_deleted` UInt8
+)
+ENGINE = ReplacingMergeTree(eventTime, is_deleted)
+ORDER BY key;
+
+INSERT INTO myThirdReplacingMT Values (1, 'first', '2020-01-01 01:01:01', 0);
+INSERT INTO myThirdReplacingMT Values (1, 'first', '2020-01-01 01:01:01', 1); 
+
+select * from myThirdReplacingMT final;
+
+0 rows in set. Elapsed: 0.003 sec.
+
+-- delete rows with is_deleted
+OPTIMIZE TABLE myThirdReplacingMT FINAL CLEANUP; 
+
+INSERT INTO myThirdReplacingMT Values (1, 'first', '2020-01-01 00:00:00', 0);
+
+select * from myThirdReplacingMT final; 
+
+┌─key─┬─someCol─┬───────────eventTime─┬─is_deleted─┐
+│   1 │ first   │ 2020-01-01 00:00:00 │          0 │
+└─────┴─────────┴─────────────────────┴────────────┘
+```
+
 ## Query clauses
 
 When creating a `ReplacingMergeTree` table the same [clauses](../../../engines/table-engines/mergetree-family/mergetree.md) are required, as when creating a `MergeTree` table.