Listing Records with Dates from the Last 10 Days in PostgreSQL

The SELECT statement is used to retrieve data from a table. You can specify the columns you want to see after SELECT. In this case, we'll likely want the date column, but you can select other columns as well.

Specifying the Table:

After SELECT, you mention the table name from which you want to retrieve data. Replace "Table" with the actual name of your table.

Filtering by Date:

The WHERE clause is used to filter the data based on specific conditions. Here, we want to filter by date.

Using Current Date and Intervals:

PostgreSQL provides the CURRENT_DATE function to get the current date. We can subtract an interval from the current date to get a date in the past. The INTERVAL keyword is used to define this time difference. In this case, the interval is '10 days'.

Filtering for Dates Greater Than:

We use the > operator to compare the date in our table with the date calculated earlier. This ensures we only select records where the date is greater than (i.e., within) the last 10 days.

Putting it all together:

Here's the complete SQL query:

SELECT *  -- Replace * with specific columns if needed
FROM Table
WHERE date > CURRENT_DATE - INTERVAL '10 days';

This query will select all columns (you can replace * with specific columns) from the table named "Table" where the "date" column is within the last 10 days (including today).

Additional Notes:

• Make sure the date in your table is stored in a format compatible with PostgreSQL's date functions.
• To be extra cautious and only include full days within the last 10 days, you can subtract an additional day from the interval. This ensures records from exactly 10 days ago aren't excluded if the time portion of the date is after a certain time. You can achieve this by using INTERVAL '10 days - 1 day'.

This code selects all columns (*) from the table named "orders" where the "order_date" is within the last 10 days:

SELECT *
FROM orders
WHERE order_date > CURRENT_DATE - INTERVAL '10 days';

This code selects only the "customer_id" and "order_date" columns from the table named "sales" where the "sale_date" is within the last 10 days (including an extra day subtraction for exact days):

SELECT customer_id, sale_date
FROM sales
WHERE sale_date > CURRENT_DATE - INTERVAL '10 days - 1 day';

The date_trunc function truncates a timestamp or date value to a specified unit. Here's how you can use it:

SELECT *
FROM your_table
WHERE date_trunc('day', your_date_column) >= date_trunc('day', CURRENT_DATE - INTERVAL '10 days');

This approach truncates both the "your_date_column" and the current date minus the interval to the day unit. This ensures you only compare full days within the last 10 days.

Using Window Functions (More Advanced):

Window functions allow calculations within a set of rows. Here's an example using dense_rank:

WITH ranked_data AS (
  SELECT *,
         dense_rank() OVER (ORDER BY your_date_column DESC) AS rank
  FROM your_table
)
SELECT *
FROM ranked_data
WHERE rank <= 10;

This method creates a temporary table alias (ranked_data) that assigns a rank to each row based on the "your_date_column" in descending order. The final SELECT retrieves only rows with a rank less than or equal to 10 (i.e., within the last 10 days).

Choosing the Right Method:

• The first method with CURRENT_DATE - INTERVAL is generally simpler and easier to understand.
• The date_trunc method can be useful if you specifically want to work with full days within the last 10 days.
• Window functions offer more advanced capabilities for complex filtering based on rankings, but they might require a deeper understanding of these functions.