Conditional Creation of a Points Table in PostgreSQL

Data and Databases
1

I am a beginner in SQL looking for some helpful advice on filtering data during table creation. I need to build a new table that only includes point entries when a specific condition is met (specifically, when the second column equals ‘01’). My current method works without this condition, but incorporating it into the point generation process has proven challenging. Any recommendations or insights on how to properly structure this query would be greatly appreciated.

CREATE TABLE new_schema.point_data AS
SELECT 
    t.a_field, 
    t.b_field, 
    p.generated_geom
FROM source_table t,
     LATERAL unnest_points(st_point_maker(t.geom_data, CAST(t.a_field AS INTEGER))) AS p(generated_geom)
WHERE t.b_field = '01';
2

hey, have u tried filtering via inner join befor lateral? i found sometimes ordering the casted parameters helps. double-checking columt data types might also clear issues. what do u think about testing explicit type casts?

3

I recently encountered a similar situation where the condition seemed to filter out more data than expected. In my experience, confirming the data type and eliminating any hidden discrepancies such as trailing spaces in the column value made a noticeable difference. Using functions like TRIM to normalize the data before comparing it to the filter value resolved the issue in one of my projects. Meticulous verification of data formats often illuminates subtle points that disrupt the intended query behavior, ensuring more predictable outcomes.

4

hey, i solved it by adding a subselect to filter t.b_field before the lateral join. sometimes faulty data (like stray spaces & wrong casing) messes things up in unnest. maybe check those details too. cheers!