How to combine multiple tables and allow a "like" text search option for filtering, including if the criteria was left blank - postgresql

Question

I have 3 different tables where I want to be able to combine them and then filter them based off of 4 different inputs OR LESS on a search. I also would like to have it work when some filters are none.. Here is the breakdown what I mean:
So above there are three tables with column names and some data. NOTE: Table 1 has a comma in the location and I will want to separate those as two separate column for searching purposes which I figured out how to do.
Now What the final table I want is:
Table 1
------------------------------------------------
date city state title summary
jan 1 stl MO Book
jan 1 ATL MO Comp
Jan 1 Maine Phone box device
March2 MO Howey weird name
JUL2 cheese
Now My goal is trying to do a text search such as what follows: The 4 criteria of filtering will be State, Title, Date, OR a keyword
I think the solution has involves joining the tables, splitting the comma, using "where true" and having some type of IF statement.
select
date1,
split_part(location1, ',', 1) as city,
split_part(location1, ',', 2) as state,
title1
from
table1
Now I use join or union or something to add other tables?
Note: Null means user didn't have input at all
Example 1: If Date is Jan 1, state is null, title is null, Keyword is null (it should show everything with jan1st)
Example 2: If Date is Jan 1 AND City is stl (show first row), title and keyword is null
Example 3: If Date = Jan 1 and State is MO (Show row 1,2, and 4), title and keyword is null
Last example: if Keyword is Phone and everything else is null it shows row 3.
Is there a way to do this in Postgressql? It also would be convenient if the user didnt spell a state right but still pulled up similar results. Basically I will have a interface where a user will select a date, or title and/or state, or maybe just use a key word to filter the results

Answer 1

Your first task is to build a combined view of the tables involved supplying null for each that does not exit in a particular table. The following uses a CTE consisting of union of the 3 tables to accomplish that.
with combined as
(Select date1 as con_date
, split_part(location1, ',', 1) as city
, split_part(location1, ',', 2) as state
, title1 as title
, null as summary
from table_1
union all
select date2
, state
, null
, title2
, null
from table_2
union all
select date3
, null
, null
, title
, null
from table_3
)
select * from combined;
From there you can build a VIEW using the above then construct an appropriate query for the entered parameters. An alternative is a function that returns a table as below.
create or replace function search_combined(
search_date_in date default null
, search_title_in text default null
, search_state_in text default null
, search_word_in text default null
)
returns table (con_date date
, city text
, state text
, title text
, summary text
)
language sql
as $$
with combined as
(Select date1 as con_date
, split_part(location1, ',', 1) as city
, split_part(location1, ',', 2) as state
, title1 as title
, null as summary
from table_1
union all
select date2
, state
, null
, title2
, null
from table_2
union all
select date3
, null
, null
, title
, null
from table_3
)
select *
from combined
where 1=1
and (con_date = search_date_in or search_date_in is null)
and (state = search_state_in or search_state_in is null)
and (title = search_title_in or search_title_in is null)
and (title = search_word_in or search_word_in is null);
$$;
-- Test
select search_combined(search_date_in => date '2019-01-01');
or
select *
from search_combined(search_date_in => date '2019-01-01');
select *
from search_combned(search_date_in => date '2019-01-01'
,search_state_in => 'Mo'
);
select *
from search_combined( search_word_in => 'Phone');
The above should work as is, but I have not tested it as your sample data is a picture. In the future please provide sample data as text; as that allows copy/past to build it locally.