


How to Dynamically Generate a CASE Statement in Postgres for Date-Based Set Assignment?
Splitting Given Strings
To split the given dates (p_dates) and sets (p_sets), we can utilize the string_split() function of Postgres. string_split() takes two arguments: the input string to be split and a delimiter.
SELECT string_split(p_dates, ','); SELECT string_split(p_sets, ',');
This will return two arrays containing the split dates and sets.
Preparing Dynamic Case Statement
To prepare a dynamic case statement, we can loop through the split arrays and construct the statement using a CASE expression.
DECLARE p_dates TEXT := '2001-01-01to2001-01-05,2001-01-10to2001-01-15'; p_sets TEXT := 's1,s2'; CASE_STATEMENT TEXT := 'CASE '; BEGIN FOR p_date IN SELECT * FROM string_split(p_dates, ',') LOOP CASE_STATEMENT := CASE_STATEMENT || 'WHEN given_dates BETWEEN ' || quote_literal(p_date) || ' ' || ... END LOOP; FOR p_set IN SELECT * FROM string_split(p_sets, ',') LOOP CASE_STATEMENT := CASE_STATEMENT || 'THEN ' || quote_literal(p_set) || ' ' END LOOP; -- Complete Case Statement with ELSE clause to assign NULL if no match CASE_STATEMENT := CASE_STATEMENT || 'ELSE NULL' || ' END'; END; SELECT CASE_STATEMENT;
The resulting CASE_STATEMENT will be a dynamic case expression that assigns appropriate set names based on the given date ranges.
CASE WHEN given_dates BETWEEN '2001-01-01' AND '2001-01-05' THEN 's1' WHEN given_dates BETWEEN '2001-01-10' AND '2001-01-15' THEN 's2' ELSE NULL END
You can use this dynamic CASE_STATEMENT in your update query to assign set names as per the given date ranges and set names.
The above is the detailed content of How to Dynamically Generate a CASE Statement in Postgres for Date-Based Set Assignment?. For more information, please follow other related articles on the PHP Chinese website!

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