The Module $4$ assignment provides practice with SQL statements for data integration. A file in the same website item contains table definitions for the problems. Problems $1$ to $9$ involve Oracle SQL for the MERGE and multiple table INSERT statements. Problems $10$ to $12$ involve the INSERT $...$ ON CONFLICT statement for PostgreSQL. You are encouraged to use both DBMSs to complete the assignment. If you only have one DBMS installed, you should provide your best solution without execution for statements using the other DBMS$.$

$1.$ Write an Oracle SQL MERGE statement to combine the SSItem dimension table and the SSItemChanges$1$ change table. The associated document contains CREATE TABLE and INSERT statements for both tables. Each matching row of SSItemChanges$1$ contains values for both modified and non$-$modified columns.

$2.$ Write an Oracle SQL MERGE statement to combine the SSItem dimension table and the SSItemChanges$2$ change table. The associated document contains CREATE TABLE and INSERT statements for both tables. Each matching row of SSItemChanges$2$ contains new values for modified columns and null values for non$-$modified columns.

$3.$ Write an Oracle SQL INSERT ALL statement to insert rows of the ProductSale$1$ table into four tables $($ProductSales$2018,$ ProductSales$2019,$ ProductSales$2020,$ and ProductSales$2021).$ The associated document contains CREATE TABLE and INSERT statements for all tables. Note that the target tables lack the SalesYear column. If SalesYear equals $2018,$ insert a row into ProductSales$2018.$ The comparisons for the other tables only differ on the SalesYear value and suffix in the name of the target table. You should compute the SalesAmt column in each target table as the sum of the quarter sales $($Qtr$1,$ Qtr$2,$ Qtr$3,$ and Qtr$4)$ in the corresponding row of the ProductSale table.

$4.$ On Problem $3,$ is the number of the rows in the target tables the same when using INSERT FIRST versus INSERT ALL? Justify your answer by writing and executing an INSERT FIRST statement.