Variables or Functions in Postrgres - postgresql

Question

I have the following code that gets the monthly resignation rate of people in a company
---2021
Select
c.id,
c.name as Company,
------January
round(cast( float8 (CASE
--employeesatendof2021
((Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date Between '0001-01-01 00:00:00' and '2021-12-31 00:00:00'
and e.terminated_at is null
and p.is_support = false)
+
(Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date is null
and e.terminated_at is null
and p.is_support = false))
WHEN 0 THEN null
Else
--eMPLOYEEsEPARATIONS2021
(Select count(e2.id) from employee e2
inner join person p2 on e2.person = p2.id
where e2.company = c.id
and e2.terminated_at at time zone l.timezone Between '2021-01-01 00:00:00' and '2021-1-31 24:00:00'
and p2.is_support = false)::numeric /
--employeesatendof2021
((Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date Between '0001-01-01 00:00:00' and '2021-12-31 00:00:00'
and e.terminated_at is null
and p.is_support = false)
+
(Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date is null
and e.terminated_at is null
and p.is_support = false))* 100
end)as numeric),2) as January_Resignation_Rate,
----February
round(cast( float8 (CASE
--employeesatendof2021
((Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date Between '0001-01-01 00:00:00' and '2021-12-31 00:00:00'
and e.terminated_at is null
and p.is_support = false)
+
(Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date is null
and e.terminated_at is null
and p.is_support = false))
--employeeSeaprtions2021
WHEN 0 THEN null
Else
--eMPLOYEEsEPARATIONS2021
(Select count(e2.id) from employee e2
inner join person p2 on e2.person = p2.id
where e2.company = c.id
and e2.terminated_at at time zone l.timezone Between '2021-02-01 00:00:00' and '2021-2-28 24:00:00'
and p2.is_support = false)::numeric /
--employeesatendof2021
((Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date Between '0001-01-01 00:00:00' and '2021-12-31 00:00:00'
and e.terminated_at is null
and p.is_support = false)
+
(Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date is null
and e.terminated_at is null
and p.is_support = false))* 100
end)as numeric),2) as February_Resignation_Rate,
CASE l.locale
WHEN 'en-AU' THEN 'Australia'
WHEN 'en-SA' THEN 'South Africa'
WHEN 'en-SG' THEN 'Singapore'
WHEN 'en-NZ' THEN 'New Zealand'
WHEN 'en-HK' THEN 'Hongkong'
WHEN 'en-UK' THEN 'United Kingdom'
end as locale
from company c
inner join location l on l.company = c.id and l.parent = 0
where l.locale = 'en-AU'
and c.id = 2
It works fine and does what it's supposed to do
But I've been using and hard coding this part of the code alot
--employeesatendof2021
((Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date Between '0001-01-01 00:00:00' and '2021-12-31 00:00:00'
and e.terminated_at is null
and p.is_support = false)
+
(Select count(e.id) from employee e
inner join person p on e.person = p.id
where e.company = c.id
and e.start_date is null
and e.terminated_at is null
and p.is_support = false))
And I was wondering if there is a way to save this part of the script in a variable or function that I can use through out the script without hardcoding it?

Answer 1

Here conditional input is used for retrieving data. If any input parameter value is NULL or empty string then it'll not used for searching option. Prepare a query based on requirement and store it in variable. Then use RETURN QUERY EXECUTE variable_full_query for executing the query and return result. Always keep in mind that out parameter name and data type must be matched with select column name and data type. Use setof records means it returns multiple records.
-- Function: public.rpt_member_info(character varying, character varying, character varying, character varying, character varying)
DROP FUNCTION IF EXISTS public.rpt_member_info(character varying, character varying, character varying, character varying, character varying);
CREATE OR REPLACE FUNCTION public.rpt_member_info(
IN p_officeInfoId CHARACTER VARYING,
IN p_projectInfoId CHARACTER VARYING,
IN p_memberInfoId CHARACTER VARYING,
IN p_fromDate CHARACTER VARYING,
IN p_toDate CHARACTER VARYING,
OUT member_id BIGINT,
out office_info_id bigint,
out project_info_id bigint,
OUT member_no CHARACTER VARYING,
OUT member_name CHARACTER VARYING,
OUT membership_date TIMESTAMP WITHOUT TIME ZONE)
RETURNS SETOF record AS
$BODY$
-- declare local variables
DECLARE v_prepareQuery VARCHAR(21840) DEFAULT '';
v_officeInfo VARCHAR(150) DEFAULT '';
v_projectInfo VARCHAR(150) DEFAULT '';
v_memberInfo VARCHAR(150) DEFAULT '';
refcur refcursor default 'test';
BEGIN
/**************************History**************************/
-- Name : rpt_member_info
-- Created Date (dd/MM/yyyy): 20/01/2022
-- Created By : Rahul Biswas
-- Reason :
-- Execute : SELECT * FROM rpt_member_info('101', '1', '1', '2022-01-01', '2022-01-31');
/***********************************************************/
-- prepare variable data based on given input
IF(p_officeInfoId != '' AND p_officeInfoId != 'null' AND p_officeInfoId IS NOT NULL)
THEN
v_officeInfo = CONCAT(' AND mi.office_info_id = ', p_officeInfoId, CHR(10));
END IF;
IF(p_projectInfoId != '' AND p_projectInfoId != 'null' AND p_projectInfoId IS NOT NULL)
THEN
v_projectInfo = CONCAT(' AND mi.project_info_id = ', p_projectInfoId, CHR(10));
END IF;
IF(p_memberInfoId != '' AND p_memberInfoId != 'null' AND p_memberInfoId IS NOT NULL)
THEN
v_memberInfo = CONCAT(' AND mi.id = ', p_memberInfoId, CHR(10));
END IF;
-- prepare query
v_prepareQuery := CONCAT('SELECT mi.id member_id
, mi.office_info_id
, mi.project_info_id
, mi.member_no
, mi.member_name
, mi.membership_date
FROM member_info mi
WHERE 1 = 1', CHR(10)
, v_officeInfo
, v_projectInfo
, v_memberInfo
, 'AND mi.membership_date BETWEEN ', '''', p_fromDate, '''', ' AND ', '''', p_toDate, '''', ';');
RETURN QUERY EXECUTE v_prepareQuery;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
Execute the function with specific input value
SELECT * FROM rpt_member_info('101', '1', '1', '2022-01-01', '2022-01-31');
Execute the function when a param value is null or empty. This will return all values of a particular column
SELECT * FROM rpt_member_info('', 'null', NULL, '2022-01-01', '2022-01-31');
Please check this url https://dbfiddle.uk/?rdbms=postgres_11&fiddle=e0f26dfa36b4636f70bd5267dab29979
Also use variable in a query and return result where all parameter value is available and prepare query isn't stored in a variable.
-- Function: public.rpt_member_info(character varying, character varying, character varying, character varying, character varying)
DROP FUNCTION IF EXISTS public.rpt_member_info(character varying, character varying, character varying, character varying, character varying);
CREATE OR REPLACE FUNCTION public.rpt_member_info(
IN p_officeInfoId BIGINT,
IN p_projectInfoId BIGINT,
IN p_memberInfoId BIGINT,
IN p_fromDate TIMESTAMP WITHOUT TIME ZONE,
IN p_toDate TIMESTAMP WITHOUT TIME ZONE,
OUT member_id BIGINT,
out office_info_id bigint,
out project_info_id bigint,
OUT member_no CHARACTER VARYING,
OUT member_name CHARACTER VARYING,
OUT membership_date TIMESTAMP WITHOUT TIME ZONE)
RETURNS SETOF record AS
$BODY$
-- declare local variables
DECLARE v_prepareQuery VARCHAR(21840) DEFAULT '';
v_officeInfo VARCHAR(150) DEFAULT '';
v_projectInfo VARCHAR(150) DEFAULT '';
v_memberInfo VARCHAR(150) DEFAULT '';
refcur refcursor default 'test';
BEGIN
/**************************History**************************/
-- Name : rpt_member_info
-- Created Date (dd/MM/yyyy): 20/01/2022
-- Created By : Rahul Biswas
-- Reason :
-- Execute : SELECT * FROM rpt_member_info(101, 1, 1, '2022-01-01', '2022-01-31');
/***********************************************************/
-- execute query
RETURN QUERY SELECT mi.id member_id
, mi.office_info_id
, mi.project_info_id
, mi.member_no
, mi.member_name
, mi.membership_date
FROM member_info mi
WHERE mi.office_info_id = p_officeInfoId
AND mi.project_info_id = p_projectInfoId
AND mi.id = p_memberInfoId
AND mi.membership_date BETWEEN p_fromDate AND p_toDate;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
Execute the function
SELECT * FROM rpt_member_info(101, 1, 1, '2022-01-01', '2022-01-31');
Please check this url https://dbfiddle.uk/?rdbms=postgres_11&fiddle=7c8ed1d02f51f5df4e263cc36a2d50e8