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A guide on how to effectively add a new column to your SQL query results, including manual entry of values. Learn techniques using `INSERT` and `UNION`.
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How to Add a New Column to Your SQL Query Results with Custom Values

In the world of SQL, sometimes you may need to modify your query results by adding new columns or enhancing existing ones. One common situation is when you want to associate some custom values with numerical results, such as summing quantities. This guide will guide you through adding a new column to your SQL results and manually inserting values into it.

Understanding the Problem

Let's start with a scenario. Suppose you have a table containing orders, and you want to display a summary of the quantities sold along with a custom name associated with each summary. For instance, you want to transform your SQL output from something like this:

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into a more informative format like this:

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In this transformed result, you have a Key column on the left that contains names you want to assign manually.

The Solution

Step 1: Creating a New Table (if Needed)

If you don’t have a suitable table to insert your results into, you can create a new one. It's good practice to separate these results from the original data for clarity. Here's how you can create a new table called orders_1_example with two columns: Key and Sum.

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Step 2: Using the INSERT and SELECT Statements

To add your custom Key values along with the sums from the orders_1 table, you can use the INSERT combined with SELECT and UNION ALL. Here's how to write the query:

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Explanation of the SQL Query

INSERT INTO orders_1_example (Key, Sum): This defines the target table and the columns where the data will go.

SELECT 'Flash disk', SUM(quantity) AS sum FROM orders_1: This part selects the first row with the custom key 'Flash disk' and calculates the total sum of quantities from the orders_1 table.

UNION ALL: This clause is used to combine the result of multiple SELECT statements. In this case, it allows you to add another row for 'mouse' with its corresponding sum.

SELECT 'mouse', SUM(quantity * priceEach) FROM orders_1: This selects the second row with a custom key 'mouse', calculating the total based on the quantity and price.

Alternative: Adding a Column to an Existing Table

If instead of creating a new table, you wish to modify the existing orders_1 table by adding the Key column directly, you can do so using the ALTER TABLE command. Here’s how to achieve that:

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After adding the column, you can insert the values similarly:

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Final Thoughts

Using SQL to manipulate and enhance your data can be straightforward once you understand the necessary commands and their functions. Whether creating a new table for your results or adding a custom column to an existing one, you've learned how to incorporate unique identifiers into your SQL outputs effectively.

By following these steps, you can ensure that your query results are not only informative but also tailored to your specific reporting needs. Don't hesitate to experiment with different queries to find the solution that best fits your scenario!