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Can anyone point out how to check if a select query returns non empty result set? For example I have next query: SELECT * FROM service s WHERE s.service_id = ?; Should I do something like next: ISNULL(SELECT * FROM service s WHERE s.service_id = ?) to test if result set is not empty?
The obvious way to achieve this is create a temp table, put the results into it, test for any rows in the temp table and either return the results from the temp table or the single empty result. Another way might be to do an EXISTS against the same where clause that's in the main query before the main query is executed.
30 maj 2019 · Solution. In the steps below, I will show one option for 'Filling the Date Gap'. First a Date table is needed to cover your date range. Next, query the Date table with a LEFT JOIN to the source table. Often you will find that you do not have a Date Table.
3 gru 2021 · An easy psql solution would be to reinject the :ROW_COUNT psql variable immediately after the query into another query to return the " No value exists " text when :ROW_COUNT is zero. Example: psql -At <<EOF. select * from pg_class where false; -- sample query that returns nothing.
6 cze 2024 · Managing null or empty values in SQL is a frequent task for database developers and administrators, as these values represent missing or undefined data. It’s essential to identify them to maintain data integrity and ensure accurate query results. In this tutorial, we’ll discuss different ways to retrieve rows containing such values.
When reading data with LOAD DATA, empty or missing columns are updated with ''. To load a NULL value into a column, use \N in the data file. The literal word NULL may also be used under some circumstances.
19 maj 2021 · This article will explain what problems can occur when working with SQL NULL values and it also gives some solution recommendations to overcome these issues. What is a SQL NULL value? In terms of the relational database model, a NULL value indicates an unknown value.
