Solution:Step 1: Add year column with literal valuesUse '2023' and '2024' as string literals to add a year column in each SELECT.Step 2: Ensure both SELECTs have same columnsBoth SELECTs must have product_id, quantity_sold, and year columns for UNION ALL.Step 3: Combine with UNION ALLSELECT product_

[Solved] You have two tables:Sales_2023: product_id, quantity_soldSales_2024:... Which query correctly uses UNION ALL and also adds a column year to identify the source year? | SQL

SQL - Set Operations

You have two tables:

Sales_2023: product_id, quantity_sold
Sales_2024: product_id, quantity_sold

You want to create a combined list of all sales including duplicates for analysis. Which query correctly uses UNION ALL and also adds a column year to identify the source year?

ASELECT product_id, quantity_sold, 'year' FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, 'year' FROM Sales_2024;

BSELECT product_id, quantity_sold FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, '2024' AS year FROM Sales_2024;

CSELECT product_id, quantity_sold, year FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, year FROM Sales_2024;

DSELECT product_id, quantity_sold, '2023' AS year FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, '2024' AS year FROM Sales_2024;

Step-by-Step Solution

Solution:

Step 1: Add year column with literal values
Use '2023' and '2024' as string literals to add a year column in each SELECT.
Step 2: Ensure both SELECTs have same columns
Both SELECTs must have product_id, quantity_sold, and year columns for UNION ALL.
Step 3: Combine with UNION ALL
SELECT product_id, quantity_sold, '2023' AS year FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, '2024' AS year FROM Sales_2024; correctly combines both tables with year column and keeps duplicates.
Final Answer:
SELECT product_id, quantity_sold, '2023' AS year FROM Sales_2023 UNION ALL SELECT product_id, quantity_sold, '2024' AS year FROM Sales_2024; -> Option D
Quick Check:
Matching columns with year literals + UNION ALL = D [OK]

Quick Trick: Add year as literal in both SELECTs for UNION ALL [OK]

Common Mistakes:

MISTAKES

Mismatched columns count in SELECTs
Using column name 'year' without value
Forgetting to alias literals as year

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You have two tables:

Step 1: Add year column with literal values

Step 2: Ensure both SELECTs have same columns

Step 3: Combine with UNION ALL

Final Answer:

Quick Check:

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