Trying to understand SO question http://stackoverflow.com/questions/36346246/not-understanding-python-string-strip-method

q36335724.sql

drop table "DB1";

create table "DB1" (
    lid integer,
    pid integer,
    "Date" date,
    primary key (lid)
);

insert into "DB1"(lid, pid, "Date")
 values (1, 123,'2016-01-01');

insert into "DB1"(lid, pid, "Date")
 values (2, 123,'2015-12-31'); -- fixed typo

drop table "DB2";

create table "DB2" (
    lid integer,
    lwid integer,
    "Description" char(100),
    "Value" float,
    "Time" time,
    primary key ( lid, lwid )
);

insert into "DB2"(lid, lwid, "Description", "Value", "Time")
 values (1, 1, 'abc', 1.0, '08:00:00');
 
insert into "DB2"(lid, lwid, "Description", "Value", "Time")
 values (2, 2, 'abc', 0.8, '03:00:00');
 
insert into "DB2"(lid, lwid, "Description", "Value", "Time")
 values (2, 3, 'abc', 0.5, '06:00:00');
 
select * from "DB1";

select * from "DB2";

-- inner select
SELECT "PID", "Description", MAX("Time"), "Value" 
FROM "DB1" SL
    INNER JOIN "DB2" SLW ON SL."LID" = SLW."LID"
WHERE   SL."Date" = '2015-12-31'
GROUP BY "PID", "Description", "Value";

-- returns
-- 	    PID	Description	MAX(Time)	Value
--  1   123	abc         03:00:00	0.8
--  2   123	abc         06:00:00	0.5

SELECT 
*
FROM "DB1" L
    INNER JOIN "DB2" LW   ON   L."LID" = LW."LID"

    LEFT JOIN (
        SELECT "PID", "Description", MAX("Time"), "Value" 
        FROM "DB1" SL
            INNER JOIN "DB2" SLW ON SL."LID" = SLW."LID"
        WHERE   SL."Date" = '2015-12-31'
        GROUP BY "PID", "Description", "Value"
    ) L1 
        ON  L1."Description" = LW."Description" 
        AND L1."PID" = L."PID"

WHERE L."PID" = 123 AND L."Date" = '2016-01-01'

-- returns
-- 	    LID	PID	Date
-- 1    1	123	01.01.16
-- 2    2	123	31.12.15

-- no error