Merge pull request #5622 from segmentio/add-retl-faq-1

Add 1 FAQ for rETL

Author: stayseesong

src/connections/reverse-etl/index.md

@@ -298,3 +298,8 @@ Column count | The maximum number of columns a single sync will process. | 512 c
 Column name length | The maximum length of a record column. | 128 characters
 Record JSON size | The maximum size for a record when converted to JSON (some of this limit is used by Segment). | 512 KiB
 Column JSON size | The maximum size of any single column value. | 128 KiB
+
+## FAQs
+
+#### Why do my sync results show *No records extracted* when I select *Updated records* after I enable the mapping? 
+It's expected that when you select **Updated records** the records do not change after the first sync. During the first sync, the reverse ETL system calculates a snapshot of all the results and creates records in the `_segment_reverse_etl` schema. All the records are considered as *Added records* instead of *Updated records* at this time. The records can only meet the *Updated records* condition when the underlying values change after the first sync completes.