[release-20.0-rc] release notes: update dml related release notes (#1…

…6241) (#16246)

Signed-off-by: Harshit Gangal <[email protected]>
Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

changelog/20.0/20.0.0/summary.md

@@ -237,37 +237,45 @@ Support is added for sharded update with limit.
 
 Example: `update t1 set t1.foo = 'abc', t1.bar = 23 where t1.baz > 5 limit 1`
 
-More details about how it works is available in [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
+The support is built on performing a selection of primary keys and then performing an update with those primary keys. 
+For query syntax, refer to the [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
 
 #### <a id="multi-table-update"/> Update with Multi Table Support
 
 Support is added for sharded multi-table update with column update on single target table using multiple table join.
 
 Example: `update t1 join t2 on t1.id = t2.id join t3 on t1.col = t3.col set t1.baz = 'abc', t1.apa = 23 where t3.foo = 5 and t2.bar = 7`
 
-More details about how it works is available in [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
+The support is built on performing a selection of primary keys and then performing an update with those primary keys.
+For query syntax, refer to the [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
 
 #### <a id="update-multi-target"/> Update with Multi Target Support
 
 Support is added for sharded multi table target update.
 
 Example: `update t1 join t2 on t1.id = t2.id set t1.foo = 'abc', t2.bar = 23`
 
-More details about how it works is available in [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
+The support is built on performing a selection of primary keys from all target tables and 
+then performing an update for each table with their selected primary keys. 
+For query syntax, refer to the [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/update.html)
 
 #### <a id="delete-subquery"/> Delete with Subquery Support
 
 Support is added for sharded table delete with subquery
 
 Example: `delete from t1 where id in (select col from t2 where foo = 32 and bar = 43)`
 
+The support is built by performing the uncorrelated subquery first and then providing the value for deletion.
+
 #### <a id="delete-multi-target"/> Delete with Multi Target Support
 
 Support is added for sharded multi table target delete.
 
 Example: `delete t1, t3 from t1 join t2 on t1.id = t2.id join t3 on t1.col = t3.col`
 
-More details about how it works is available in [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/delete.html)
+The support is built on performing a selection of primary keys from all target tables and 
+then performing a delete operation for each table with their selected primary keys. 
+For query syntax, refer to the [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/delete.html)
 
 #### <a id="udf-support"/> User Defined Functions Support
 
@@ -288,7 +296,7 @@ Example:
 - `insert into user(id, name, email) valies (100, 'Alice', '[email protected]') as new on duplicate key update name = new.name, email = new.email`
 - `insert into user(id, name, email) valies (100, 'Alice', '[email protected]') as new(m, n, p) on duplicate key update name = n, email = p`
 
-More details about how it works is available in [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html)
+For query syntax, refer to the [MySQL Docs](https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html)
 
 ### <a id="query-timeout"/>Query Timeout
 On a query timeout, Vitess closed the connection using the `kill connection` statement. This leads to connection churn