How to Dynamically Update a Table Based on Split Date Ranges and Set Names Using a Case Statement?

Split Given String and Prepare Case Statement

To efficiently update a table based on specific date ranges and corresponding set names, it's necessary to split the given strings into individual components dynamically. This approach allows for handling variable input parameters and ensures flexibility in update operations.

Splitting Date Ranges and Set Names

1. Split Date Ranges:

   • Split the p_dates parameter using a comma (,) as a delimiter. This will result in an array of date ranges in the format "start_date to end_date."

   SELECT unnest(string_to_array(p_dates, ',')) AS date_range;

2. Split Set Names:

   • Similarly, split the p_sets parameter using a comma (,) as a delimiter. This will result in an array of set names.

   SELECT unnest(string_to_array(p_sets, ',')) AS set_name;

Dynamic Case Statement Preparation

Once the date ranges and set names are split, a dynamic case statement can be constructed using the following steps:

1. Loop Through Date Ranges:

   • Iterate through the array of date ranges.

2. Extract Range Boundaries:

   • Extract the start and end dates from each range using split_part and specify the delimiter as "to."

3. Build Case Clause:

   • For each date range, use update table_name set set_name to update the corresponding set name.
   • Use the BETWEEN condition to filter the rows based on the date range.

The following code snippet demonstrates how to prepare the dynamic case statement:

PREPARE upd_tbl AS
UPDATE table_name
SET    set_name = CASE
  WHEN given_date BETWEEN split_part(, 'to', 1)::date
                       AND split_part(, 'to', 2)::date THEN 
  ELSE null
END;

Where:

• $1 is a placeholder for the date range.
• $2 is a placeholder for the corresponding set name.

By executing this prepared statement with date_range and set_name as parameters, the table can be updated based on the specified date ranges and set names.

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