$----$ Q$6$: Drop the clustered index on T$3($a$,$b$).$ Create a clustered index on T$3($b$,$a$).$ Why the column order in the index made a difference

$--$Show the new query plan and explain.

$--$ You may use the following commands to add a primary key to a table

alter table T$3$ drop constraint T$3\_$PK

alter table T$3$ add CONSTRAINT T$3\_$PK primary key $($b$,$a$)$

$--$ Q$7$: for the query below, can you elaborate on the impact of the value of @param on the query plan

$--$ Please give different values to @param, show how the query plan may change in response to the value of @param

$--$ and explain why the query optimizer decided to choose each query plan

SELECT $*$

FROM T$1$ JOIN T$2$ on T$1.$a $=$ T$2.$a JOIN T$3$ on T$1.$a $=$ T$3.$b

Where T$1.$a$>$@param