Left outer join not showing second table as null - mysql

Question

Table structre
table 1
account
123
1234
12345
123456
table 2
account
123
1234
12345
I want to return table a record 123456 on account for table1 and null for column 2 when it doesnt match table 2
SQL
SELECT table1.account, table2.account
from table1
left outer join table2
on (table1.account= table2.account)

Answer 1

Your where statement explicitly asked for non-null rows with table2.dates = '19-jul-17'
You should modify your query to check for nulls:
SELECT
table1.account, table2.account
from table1
left outer join table2
on (table1.account= table2.account)
where
t1.dates='20170719'
and ( table2.account is NULL
or
table2.dates = '20170719'
)
This matches rows that have a specific date in the first table, and either null or a specific date on the second.
Note the date literal. The original query used a locale-specific format. This can fail easily faile in locales that don't use that format. Never mind the two digit year.
YYYYMMDD on the other hand is unambiguous.
UPDATE
Once the where clause is removed, NULLs are returned as expected :
declare #table1 table (id int)
declare #table2 table (id int)
insert into #table1
values
(123 ),
(1234 ),
(12345 ),
(123456)
insert into #table2
values
(123 ),
(1234 ),
(12345)
SELECT t1.id, t2.id
from #table1 t1
left outer join #table2 t2
on (t1.id= t2.id)
Returns
id id
123 123
1234 1234
12345 12345
123456 NULL
If the question is "how do I get the non-matching row" the answer is use WHERE tabl2.ID IS NULL

Answer 2

Everything is OK in your query, If you are using any where clause, please remove and check, BTW i am not able to reproduce your issue. PFB attempt, The query gives expected result
create table #tmp1( ID int)
create table #tmp2( ID int)
Insert into #tmp1 values('123')
Insert into #tmp1 values ('1234')
Insert into #tmp1 values ('12345')
Insert into #tmp1 values ('123456')
Insert into #tmp2 values('123')
Insert into #tmp2 values ('1234')
Insert into #tmp2 values ('12345')
select * from #tmp1
select * from #tmp2
SELECT #tmp1.ID, #tmp2.ID from #tmp1 left outer join #tmp2 on (#tmp1.ID=#tmp2.ID)
drop table #tmp1
drop table #tmp2
The result is:
ID ID
123 123
1234 1234
12345 12345
123456 NULL