Union null in Oracle - sql

Question

I'm trying to combine 2 querys in oracle, those lines have the same value expect one field.
Ex:
SELECT NAME, AGE, EMAIL, DATE FROM table_a WHERE NAME = 'JOAO' AND FLAG = '0'
UNION
SELECT NAME, AGE, EMAIL, DATE FROM table_a WHERE NAME = 'JOAO' AND FLAG = '1'
Result:
NAME AGE EMAIL DATE
JOAO 23 a#a.com 20150414
JOAO 23 a#a.com null
How i can group this lines?? I'm looking for something who can give me something like this result:
NAME AGE EMAIL DATE
JOAO 23 a#a.com 20150414
Thank you
(sorry for my english..)

Answer 1

You can use COALESCE(). http://docs.oracle.com/cd/B28359_01/server.111/b28286/functions023.htm#SQLRF00617/ms190349.aspx
This Query should work for every name, and should coalesce the other rows.
SELECT
NAME1 AS NAME,
COALESCE(AGE1, AGE2) AS AGE,
COALESCE(EMAIL1, EMAIL2) AS EMAIL,
COALESCE(DATE1, DATE2) AS DATE
FROM(
SELECT
t1.NAME AS NAME1,
t1.AGE AS AGE1,
t1.EMAIL AS EMAIL1,
t1.DATE AS DATE1,
t2.NAME AS NAME2,
t2.AGE AS AGE2,
t2.EMAIL AS EMAIL2,
t2.DATE AS DATE2
FROM table_a AS t1
INNER JOIN table_a AS t2
ON t2.FLAG = 1 AND t1.FLAG = 0 AND t1.NAME = t2.NAME
) AS t3;

Answer 2

It would be the case to change your conditions in the 'WHERE' clause from
WHERE NAME = 'JOAO' AND FLAG = '0'
to
WHERE NAME = 'JOAO' AND FLAG IN('0','1')
so your selection shows all the registers with either '0' or '1' values for the column 'FLAG'.

Answer 3

If you're just trying to ignore the NULL values:
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG in ( '0', '1' )
and date is not null
/
or
if you want to keep the nulls, but defer to available non-null values:
with w_data as (
SELECT NAME, AGE, EMAIL, DATE ,
row_number() over ( partition by name
order by date desc nulls last ) rnum
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG in ( '0', '1' )
)
select name, age, email, date
from w_data
where rnum = 1
/
[edit]
in response to comment:
If you want to keep union, that's fine, union and OR are mostly interchangeable (in this case):
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '0'
and date is not null
union
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '1'
and date is not null
/
or even:
select * from (
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '0'
union
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '1'
)
where date is not null
/
if you just want the NULL criteria in 1 place ;)
Same logic can apply to the 2nd query I wrote above using row_number() analytics ...
with w_data as (
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '0'
union
SELECT NAME, AGE, EMAIL, DATE
FROM table_a
WHERE NAME = 'JOAO'
AND FLAG = '1'
),
w_sub as (
select name, age, email, date,
row_number() over ( partition by name
order by date desc nulls last ) rnum
from w_data
)
select name, age, email, date
from w_sub
where rnum = 1
/