How to Update Rows with Unique Date-Price Combinations in a Sales Table?

Updating Sales Records with Unique Date-Price Combinations

This guide demonstrates how to identify and update sales records that possess unique price-date combinations within a sales table. The objective is to update only those sales entries without any duplicates sharing the same price and date.

One method involves a two-step process using SQL queries:

Step 1: Identifying Unique Combinations

The following query selects unique saleprice and saledate combinations, along with their corresponding id and the count of occurrences:

<code class="language-sql">SELECT DISTINCT saleprice, saledate, id, COUNT(*) AS count
FROM sales
GROUP BY saleprice, saledate
HAVING COUNT(*) = 1;</code>

This query groups sales records by saleprice and saledate, then filters the results using HAVING to retain only those groups with a count of one, signifying unique combinations.

Step 2: Updating the Sales Table

To update the status of these unique sales records to 'ACTIVE', utilize the following query:

<code class="language-sql">UPDATE sales
SET status = 'ACTIVE'
WHERE id IN (
    SELECT id
    FROM sales s
    INNER JOIN (
        SELECT saleprice, saledate
        FROM sales
        GROUP BY saleprice, saledate
        HAVING COUNT(*) = 1
    ) AS unique_sales ON s.saleprice = unique_sales.saleprice AND s.saledate = unique_sales.saledate
);</code>

This query updates the sales table, setting the status to 'ACTIVE' for records whose id matches those identified in the subquery. The subquery efficiently retrieves the id values associated with unique saleprice and saledate combinations. The INNER JOIN ensures that only matching records are updated.

This approach leverages the power of GROUP BY and HAVING clauses to effectively perform distinct selection across multiple columns and achieve the desired updates.

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