How to check the query has values and get the difference of the start date and end date in intervals in postgres SQL? - postgresql

Question

These are the summary of issue:
There is an issue of not going inside the if clause and data not inserted.
Need to compute the target_progress_date as the difference between the end_date and start_date and all the interval months to be computed and stored in the variable so as to insert into the project_target_progress table.
Viz: Start date :1-1-2021, End date : 1-12-2021 Months: 1-1-2021
1-2-2021 1-3-2021 .... 12-12-2021
// To check if any values are there
$query_check = pg_query(DBCON,"select id , (COALESCE(revised_cost,administrative_sanction_project_cost,award_tender_project_cost) as cost, COALESCE(award_tender_contract_date,administrative_sanction_date,actual_start_date) as start_date, COALESCE(revised_completion_date,scheduled_completion_date)::date) as end_date from sp_index_v4 where id = $proj_id ");
// If it has no null values then execute the logic - Autoset of target progress before editing it.
if ($query_check != null) {
console.log ('Hi'+$query_check);
$query_cost = pg_query(DBCON,"select id ,(COALESCE(revised_cost,administrative_sanction_project_cost,award_tender_project_cost)/ datediff('month',COALESCE(award_tender_contract_date,administrative_sanction_date,actual_start_date)::date, COALESCE(revised_completion_date,scheduled_completion_date)::date)) as cost_of_one_month, TRUNC(((COALESCE(revised_cost,administrative_sanction_project_cost,award_tender_project_cost)/ datediff('month',COALESCE(award_tender_contract_date,administrative_sanction_date,actual_start_date)::date, COALESCE(revised_completion_date,scheduled_completion_date)::date))/ (COALESCE(revised_cost,administrative_sanction_project_cost,award_tender_project_cost)))*100,2) as cost_percent from sp_index_v4 id = $proj_id");
// Insert for new project entry update for already having project
$ins_query = "insert into project_target_progress(project_id,cum_financial_progress_in_cr,cum_financial_progress_in_percent,cum_physical_progress_in_percent,target_progress_date)values('$id',cost_of_one_month,cost_percent,cost_percent,start_date)";
$insert_data = pg_query(DBCON, $ins_query);
}
else {
echo "Value cannot be inserted";
console.log("inside the else block");
}

Answer 1

I wrote my own datediff function with different opportunities:
create or replace function datediff
(
units varchar(30),
start_t timestamp,
end_t timestamp
)
returns int as $$
declare
diff_interval interval;
diff int = 0;
years_diff int = 0;
begin
if units in ('yy', 'yyyy', 'year', 'mm', 'm', 'month') then
years_diff = date_part('year', end_t) - date_part('year', start_t);
if units in ('yy', 'yyyy', 'year') then
return years_diff;
else
return years_diff * 12 + (date_part('month', end_t) - date_part('month', start_t));
end if;
end if;
diff_interval = end_t - start_t;
diff = diff + date_part('day', diff_interval);
if units in ('wk', 'ww', 'week') then
diff = diff/7;
return diff;
end if;
if units in ('dd', 'd', 'day') then
return diff;
end if;
diff = diff * 24 + date_part('hour', diff_interval);
if units in ('hh', 'hour') then
return diff;
end if;
diff = diff * 60 + date_part('minute', diff_interval);
if units in ('mi', 'n', 'minute') then
return diff;
end if;
diff = diff * 60 + date_part('second', diff_interval);
return diff;
end;
$$ language plpgsql;
Now, we can write a sample query using our function:
select
mm.start_date,
mm.end_date,
test.datediff('year', mm.start_date, mm.end_date) as diff_year,
test.datediff('month', mm.start_date, mm.end_date) as diff_month,
test.datediff('day', mm.start_date, mm.end_date) as diff_day
from (
select '2021-11-25 02:20:54.200'::timestamp as start_date, now()::timestamp as end_date
) mm
Result:
start_date
end_date
diff_year
diff_month
diff_day
2021-11-25 02:20:54.200
2022-02-24 06:10:52.258
1
3
91