I have two tables Table A and Table B
Table A
1. *id*
2. *name*
Table B
1. *A.id*
2. *datetime*
I want to select
1. *A.id*
2. *A.name*
3. *B.datetime*
Even if table B do not contains a row with A.id for specific day and it should replace that column with NULL
e.g
Table A contains
1. *(1 , Haris)*
2. *(2, Hashsim)*
Table B Contains following for today's date.
1. *(1, '2014-12-26 08:00:00')*
I should show 2 results with id 1 and 2 instead of only id 1.
Using LEFT OUTER JOIN with WHERE Clause makes it a LEFT INNER JOIN, how to work around that ?
SELECT A.id, A.name, b.datetime
FROM A
LEFT Outer JOIN B on B.id = A.id
Use LEFT OUTER JOIN to get all the rows from Left table and one that does not have match will have NULL values in Right table columns
SELECT A.id,
A.name,
B.[datetime]
FROM tableA A
LEFT OUTER JOIN tableB B
ON A.Id = B.id
AND B.[datetime] < #date
SELECT a.id, a.name, b.datetime
FROM A
LEFT JOIN B on B.aid = a.id
WHERE coalesce(B.datetie, '1900-01-01') < #MyDateTime
Select A.id,A.name,B.datetime
from tableA A
Left join
(
SELECT B.ID,B.datetime
FROM tableB B
WHERE B.datetime <= 'myDateTime'
)B
ON A.aid = B.id
Related
I am kind of stuck at one problem at my job where I need to pull 2 cols from base table and 1 column from a series of joins.
Please note that, I can not provide real data so I am using dummy column/table names and there are 100s of columns in real project.
Select A.Name,B.Age, D.Sal
From A Left join B on A.iD=B.id and B.Date=CURRENT_DATE
(/* join A and B table and return distinct column which is B.XYZ)
inner join C on C.iD=B.XYZ
(/* join B and C take C.YYY column for next join */)
inner join D on D.id=C.YYY
(/* Take out the D.Sal column from this join */) where A.Dept='IT'
I have written this query but it is taking forever to run because B.XYZ column has a lot of duplicates. how can I get distinct of B.XYZ column from that join.
For Joining Table B, you first get a distinct table of the columns you need from B then join.
SELECT
A.Name,
B.Age,
D.Sal
From A
LEFT JOIN ( -- Instead of all cols (*), just id, Date, Age and xyz might do
SELECT DISTINCT * FROM B
) B ON A.iD = B.id AND B.Date = CURRENT_DATE
--(/* join A and B table and return distinct column which is B.XYZ */)
INNER JOIN C ON C.iD = B.XYZ
--(/*join B and C take C.YYY column for next join */)
INNER JOIN D ON D.id = C.YYY
--(/* Take out the D.Sal column from this join */)
WHERE A.Dept='IT'
You say you get the same rows multifold, because for a b.id, date and age you get the same xyz more than once, or so I understand it.
One option is to join with a subquery that gets the distinct data:
SELECT a.name, b.age, d.sal
FROM a
LEFT JOIN
(
SELECT DISTINCT id, date, age, xyz FROM b
) dist_b ON dist_b.id = a.id and dist_b.date = CURRENT_DATE
INNER JOIN c ON c.id = dist_b.xyz
INNER JOIN d ON d.id = c.yyy
WHERE a.dept = 'IT';
Of course you can even move the date condition inside the subquery:
SELECT a.name, b.age, d.sal
FROM a
LEFT JOIN
(
SELECT DISTINCT id, age, xyz FROM b WHERE date = CURRENT_DATE
) dist_b ON dist_b.id = a.id
INNER JOIN c ON c.id = dist_b.xyz
INNER JOIN d ON d.id = c.yyy
WHERE a.dept = 'IT';
Your LEFT OUTER JOIN doesn't work by the way. As you are inner joining the following tables, a match must exists, so your outer join becomes an inner join. For the outer join to work you would have to outer join the following tables, too.
I want to sum two tables. Both tables contain the number of rowas grouped by a category:
number category
5 A
4819 B
1 C
number category
12043 B
I tried the following:
select a.category, a.number + b.number as number
from a
right join b
on a.category = b.category
I get:
number category
4 16862
I don't understand why I don't get all three categories. I trief left join instead of right join.
The problem with you right join is that a table should appear on the right side of the join. Or, using a left join, we could write:
SELECT
a.category,
a.number + COALESCE(b.number, 0) AS number
FROM tablea a
LEFT JOIN tableb b
ON a.category = b.category;
But this answer assumes that the a table would contain every category which you want to appear in your result set. For a more general solution, we might have to use a full outer join:
SELECT
COALESCE(a.category, b.category) AS category,
COALESCE(a.number, 0) + COALESCE(b.number, 0) AS number
FROM tablea a
FULL OUTER JOIN tableb b
ON a.category = b.category;
You can use union all and aggregation:
select category ,sum(number) value
from (
select category, number from tablea
union all select category, number from tableb
)
group by category
Another option is to do a full outer join: this would allow values coming from both sides of the join:
select
coalesce(ta.category, tb.category) number,
sum(coalesce(ta.number, 0) + coalesce(tb.number, 0)) value
from tablea ta
full outer join tableb tb on ta.category = tb.category
group by coalesce(ta.category , tb.category )
I should have used nvl(). This works:
select a.category, nvl(a.number, 0) + nvl(b.number, 0) as number
from a
right join b
on a.category = b.category
I'm trying to join two tables like this:
Table A
ID Value1
1 A
2 B
3 C
Table B
ID Value2
1 A
3 B
4 C
Result should be:
ID Value1 Value2
1 A A
2 B null
3 C B
4 null C
I.e. join Table A to Table B on ID. If ID doesn't exist in Table A, add the ID from Table B.
The closest I've come is:
SELECT
a.ID, a.Value1, b.Value2
FROM
TableA a
OUTER JOIN
TableB b ON a.ID = b.ID
That gives me the new rows from TableB, but the ID is null.
How can I accomplish this?
You are very close, you just need a little push in the right direction:
SELECT COALESCE(a.ID, B.ID) As ID, a.Value1, b.Value2
FROM TableA a
FULL OUTER JOIN TableB b ON a.ID=b.ID
The COALESCE function returns the first parameter it gets that is not null. since this is a full outer join, a.id will be null on one row and b.id would be null on a different row.
Try this:
SELECT *
FROM TableA A
FULL OUTER JOIN TableB B
ON A.ID = B.ID;
Just a note: you should not name your tables in SQL with spaces in them.
Remember the basic for joining different tables
SELECT column_name(s)
FROM table1
FULL OUTER JOIN table2
ON table1.column_name=table2.column_name;
For your case:
SELECT a.value1, b.value2
FROM TableA a
FULL OUTER JOIN TableB b ON a.ID=b.ID
remember full outer join
The FULL OUTER JOIN keyword returns all rows from the table (tableA) and from the table (tableB) and the FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.
I have next tables.
First one is A.
A have two columns: A_ID and A_VALUE.
Second table is B. B too have two columns: B_ID and B_VALUE
In additional I have table C. Table C have C_ID and bool columns C_BOOL
If C_BOOL value == true i need select value from A with given ID.
If C_BOOL value == false i need select value from B.
How I can write SELECT for this?
I use oracle db.
Thanks in advice.
SELECT CASE C.BOOL WHEN 1 THEN A.ID ELSE B.ID END
FROM A
JOIN B
ON B.ID = A.ID
JOIN C
ON C.ID = A.ID
Try this query:
SELECT C_ID,CASE WHEN C_BOOL = 1 THEN T3.A_VALUE ELSE T2.B_VALUE END
FROM TABLE_C T1 LEFT OUTER JOIN TABLE_B T2 ON T1.C_ID = T2.B_ID
LEFT OUTER JOIN TABLE_A T3 T2 ON T1.C_ID = T3.A_ID
select decode(C.BOOL,1,A.ID,B.ID) FROM C
JOIN A
ON A.ID=C.ID
JOIN B
ON B.ID=C.ID;
I consider T McKeown answer as valid this is just equivalent (but more compact) I suppose.
I need to simulate the left join effect without using the "left join" key.
I have two tables, A and B, both with id and name columns. I would like to select all the dbids on both tables, where the name in A equals the name in B.
I use this to make a synchronization, so at the beginning B is empty (so I will have couples with id from A with a value and id from B is null). Later I will have a mix of couples with value - value and value - null.
Normally it would be:
SELECT A.id, B.id
FROM A left join B
ON A.name = B.name
The problem is that I can't use the left join and wanted to know if/how it is possible to do the same thing.
you can use this approach, but you must be sure that the inner select only returns one row.
SELECT A.id,
(select B.id from B where A.name = B.name) as B_ID
FROM A
Just reverse the tables and use a right join instead.
SELECT A.id,
B.id
FROM B
RIGHT JOIN A
ON A.name = B.name
I'm not familiar with java/jpa. Using pure SQL, here's one approach:
SELECT A.id AS A_id, B.id AS B_id
FROM A INNER JOIN B
ON A.name = B.name
UNION
SELECT id AS A_id, NULL AS B_id
FROM A
WHERE name NOT IN ( SELECT name FROM B );
In SQL Server, for example, You can use the *= operator to make a left join:
select A.id, B.id
from A, B
where A.name *= B.name
Other databases might have a slightly different syntax, if such an operator exists at all.
This is the old syntax, used before the join keyword was introduced. You should of course use the join keyword instead if possible. The old syntax might not even work in newer versions of the database.
I can only think of two ways that haven't been given so far. My last three ideas have already been given (boohoo) but I put them here for posterity. I DID think of them without cheating. :-p
Calculate whether B has a match, then provide an extra UNIONed row for the B set to supply the NULL when there is no match.
SELECT A.Id, A.Something, B.Id, B.Whatever, B.SomethingElse
FROM
(
SELECT
A.*,
CASE
WHEN EXISTS (SELECT * FROM B WHERE A.Id = B.Id) THEN 1
ELSE 0
END Which
FROM A
) A
INNER JOIN (
SELECT 1 Which, B.* FROM B
UNION ALL SELECT 0, B* FROM B WHERE 1 = 0
) B ON A.Which = B.Which
AND (
A.Which = 0
OR (
A.Which = 1
AND A.Id = b.Id
)
)
A slightly different take on that same query:
SELECT A.Id, B.Id
FROM
(
SELECT
A.*,
CASE
WHEN EXISTS (SELECT * FROM B WHERE A.Id = B.Id) THEN A.Id
ELSE -1 // a value that does not exist in B
END PseudoId
FROM A
) A
INNER JOIN (
SELECT B.Id PseudoId, B.Id FROM B
UNION ALL SELECT -1, NULL
) B ON A.Which = B.Which
AND A.PseudoId = B.PseudoId
Only for SQL Server specifically. I know, it's really a left join, but it doesn't SAY LEFT in there!
SELECT A.Id, B.Id
FROM
A
OUTER APPLY (
SELECT *
FROM B
WHERE A.Id = B.Id
) B
Get the inner join then UNION the outer join:
SELECT A.Id, B.Id
FROM
A
INNER JOIN B ON A.name = B.name
UNION ALL
SELECT A.Id, NULL
FROM A
WHERE NOT EXISTS (
SELECT *
FROM B
WHERE A.Id = B.Id
)
Use RIGHT JOIN. That's not a LEFT JOIN!
SELECT A.Id, B.Id
FROM
B
RIGHT JOIN A ON B.name = A.name
Just select the B value in a subquery expression (let's hope there's only one B per A). Multiple columns from B can be their own expressions (YUCKO!):
SELECT A.Id, (SELECT TOP 1 B.Id FROM B WHERE A.Id = B.Id) Bid
FROM A
Anyone using Oracle may need some FROM DUAL clauses in any SELECTs that have no FROM.
You could use subqueries, something like:
select a.id
, nvl((select b.id from b where b.name = a.name), "") as bId
from a
you can use oracle + operator for left join :-
SELECT A.id, B.id
FROM A , B
ON A.name = B.name (+)
Find link :-
Oracle "(+)" Operator
SELECT A.id, B.id
FROM A full outer join B
ON A.name = B.name
where A.name is not null
I'm not sure if you just can't use a LEFT JOIN or if you're restricted from using any JOINS at all. But as far as I understand your requirements, an INNER JOIN should work:
SELECT A.id, B.id
FROM A
INNER JOIN B ON A.name = B.name
Simulating left join using pure simple sql:
SELECT A.name
FROM A
where (select count(B.name) from B where A.id = B.id)<1;
In left join there are no lines in B referring A so 0 names in B will refer to the lines in A that dont have a match
+ or A.id = B.id in where clause to simulate the inner join