So I'm trying to write a query to pull some data and I have one condition that needs to be met and I can't seem to figure out how to actually execute it. What I'm trying to achieve is that if a column is not null in one table, then I want to check another table and see if there is a specific value in one those columns. So in a psuedo code type of way I'm trying to do this
SELECT id, user_name, created_date, transaction_number
FROM TableA
WHERE (IF TableA.response_id IS NULL OR
IF (SELECT type_id from TableB WHERE (type_id NOT IN ('4)) AND (id = TableA.response_id))
So from here what I'm trying to do is pull all transactions for customers that have no responses in them, but from those that do have responses I still want to grab transaction that's don't have a specific code associated to them. I'm not sure if it's possible to do it in this manner or if I need to create some temporary tables that can then be manipulated but I'm stuck on this one condition.
At first I thought you wanted the CASE statement from the wording of your question, but I think you're just looking for an OUTER JOIN with an OR statement:
SELECT DISTINCT a.id, a.user_name, a.created_date, a.transaction_number
FROM TableA A
LEFT JOIN TableB B ON A.response_id = B.Id
WHERE A.response_id IS NULL
OR B.type_id NOT IN (4)
A Visual Explanation of SQL Joins
where TableA.Response_id is null or (select count(1) from TableB WHERE (type_id NOT IN ('4)) AND (id = TableA.response_id)) = 0
provided that your subquery is logically correct.
Well I'm not 100% certain I follow, but assuming what you want is to see if there are response entries for a particular ID in Table A I think you want something like this.
SELECT a.id, user_name, created_date, transaction_number
FROM TableA a
LEFT JOIN TableB b
ON a.id=b.id
LEFT JOIN TableC c
ON a.id=c.id
WHERE isnull(b.id,c.id) IS NOT NULL
GROUP BY a.id, user_name, created_date, transaction_number
ISNULL will return b.id if it is not null, c.id if c.id is not null and NULL otherwise. That will tell you if there's a response for a.id in either TableB or TableC. That's assuming TableB & TableC are more like logs. If you're saying those table will certainly have an entry for a.id then it's just a matter of replacing b.id & c.id with b.[response_column] & c.[response_column] respectively.
Related
I face issue about duplicate data when join table, here my sample data table I have
-- Table A
I want to join with
-- Table B
this my query notation for join both table,
select a.trans_id, name
from tableA a
inner join tableB b
on a.ID_Trans = b.trans_id
and this the result, why I get the duplicating data which should show only two lines of data, please help me to solve this case.
Firstly, as you have been told multiple times in the comments, this is working exactly as you have written, and (more importantly) as intended. You have 2 rows in tableA and those 2 rows match 2 rows in your table tableB according to the ON clause. This means that each join operation, for the each of the rows in tableA, results in 2 rows as well; thus 4 rows (2 * 2 = 4).
Considering that your table, TableA only has one column then it seems that you should be cleaning up that data and deleting the duplicates. There are plenty of examples on how to do that already (example).
Perhaps the column you show us in TableA is one many, and thus instead you have a denormalisation issue, and instead there should be another table with the details of Id_trans and a PRIMARY KEY or UNIQUE CONSTRAINT/INDEX on it. Then you would join fron that table to TableB.
Finally, what you might be after is an EXISTS, which would look like this:
SELECT B.trans_id, B.[name]
FROM dbo.TableB B
WHERE EXISTS(SELECT 1
FROM dbo.TableA A
WHERE A.ID_Trans = B.trans_id); --Odd that it's called ID_Trans in one table, and Trans_ID in another
As the comments mentioned your query does exactly what you asked it to do but I think you wanted something like:
select a.trans_id, a.name, b.name
from tableA a
inner join tableB b on a.trans_id = b.trans_id
group by a.trans_id, a.name, b.name
Since there are two rows in both table with same ID join will make them four. You can use distinct to remove duplicates:
select distinct a.trans_id, name
from tableA a
inner join tableB b
on a.id_trans = b.trans_id
But I would suggest to use exists:
select trans_id, name
from tableB b
exists (select 1 from tableA a where a.trans_id=b.trans_id)
I need to write a stored procedures to update contacts who have no active pledges in our database, I can't seem to find a way of counting contacts with 0 rows on the pledges table.
The external key in the pledges table is supporter_id, I've tried using Count(*), but it only returns 1 or more.
Thanks in advance.
PS: This is on a MS SQL database.
We'd need more information to give you a specific answer, but there are a number of ways to identify non-matching records, here are two:
LEFT JOIN:
SELECT a.*
FROM TableA a
LEFT JOIN TableB b
ON a.ID = b.ID
WHERE b.ID IS NULL
NOT EXISTS:
SELECT *
FROM TableA a
WHERE NOT EXISTS (SELECT *
FROM TableB b
WHERE a.ID = b.ID)
I ended using a subquery so I first determine who has pledges of the type I want and then look for contacts who are not in that list.
thanks for the responses.
I saw answers to a related question, but couldn't really apply what they are doing to my specific case.
I have a large table (300k rows) that I need to join with another even larger (1-2M rows) table efficiently. For my purposes, I only need to know whether a matching row exists in the second table. I came up with a nested query like so:
SELECT
id,
CASE cnt WHEN 0 then 'NO_MATCH' else 'YES_MATCH' end as match_exists
FROM
(
SELECT
A.id as id, count(*) as cnt
FROM
A, B
WHERE
A.id = B.foreing_id
GROUP BY A.id
) AS id_and_matches_count
Is there a better and/or more efficient way to do it?
Thanks!
You just want a left outer join:
SELECT
A.id as id, count(B.foreing_id) as cnt
FROM A
LEFT OUTER JOIN B ON
A.id = B.foreing_id
GROUP BY A.id
I am doing a join between two tables and want to select the columns based on whether they have a record or not. I'm trying to avoid having multiple of the same field and am trying to condense them into single columns. Something like:
Select
id = (CASE WHEN a.id IS NULL THEN b.id ELSE a.id END),
name = (CASE WHEN a.name IS NULL THEN b.name ELSE a.name END)
From Table1 a
Left Join Table2 b
On a.id = b.id
Where a.id = #id
I'd like id to populate from Table1 if a record exists, but if not pull from Table2. The previous code returns no records because there are no NULL values in Table1 so my question is how do I run a check to see if any records even exist? Also if anyone knows of a better way to accomplish what I am trying to do I appreciate guidance and constructive criticism.
EDIT
It looks like COALESCE will work for what I'm trying to accomplish. I'd like to give a little more info on exactly what I am working with and get some advice on whether I am using the best method.
I have a bloated table Table2 and it is in production. I'm working on building new web applications for this system but can't justify a complete database redesign so I am trying to do one "on the fly". I've created a new table Table1 and I am writing stored procedures for the following methods Get(Select), Set(Update), Add(Insert), Remove(Delete). This way, to my code, it will seem that I am working with a single table that is not bloated. My code will simply call one of the SP methods and then the stored procedure will handle the data between the old table and the new. I am currently working on the Get method and I need to check the old table Table2 for a record if it doesn't exist in Table1.
Thanks to the suggestions here my query currently looks like this:
Select
id = coalesce(a.id, b.student_number),
first_name = coalesce(a.first_name, b.first_name),
last_name = coalesce(a.last_name, b.last_name),
//etc
From Table1 a
Full Outer Join Table2 b
On a.id = b.student_number
Where (a.id = #id Or b.student_number = #id)
This works for what I'm trying to accomplish, I'd like to throw it out there to the experienced crowd for any tips or suggestions if there are better or more correct ways to go about this.
Thanks
I suspect your problem may come from doing a left join. Try again using a full outer join, like this:
Select
id = coalesce(a.id, b.id),
name = coalesce(a.name, b.name)
From Table1 a
full outer Join Table2 b
On a.id = b.id
Where a.id = #id
Select id = coalesce(a.id, b.id),
name = coalesce(a.name, b.name)
From Table2 b
Left Join Table1 a On a.id = b.id
Where b.id = #id
You may need to use ISNULL or CASE instead of COALESCE depending on your database platform.
First, you don't need a case statement for that:
Select ISNULL(a.id,b.id) AS id, ISNULL(a.name,b.name) AS name,
From Table1 a
Left Join Table2 b
On a.id = b.id
Where a.id = #id
Second, if I get it right, the id field can contain nulls, and in that case you are screwed. I mean, the ID is a unique value that identify a row, if it can be null, you can't identify that row.
But if what you want is getting records from Table1 and Table2 and avoid duplicates, a simple UNION will work fine, since it discards duplicates:
select id, name
from Table1
where id = #id
union
select id, name
from Table2
where id = #id
You could do something like:
select id, name from Table1 a where a.id not in (select id from Table2)
UNION
select id, name from Table2 b
This would give you all the records from table1 that didn't have a corresponding match in table2 plus all of table2's records. The union would then combine the results.
In your first CASE statement, a.id and b.id will always be same value, except for instances in which a.id has a value and b.id generates a NULL value because of the LEFT JOIN. There will never be a row in the result set with a NULL a.id value and a non-NULL b.id value. You could just use a.id for this column.
For the second CASE statement, you may find the name column in either or both tables with a value (and, of course, the values may be different). You said you want to "condense" the these column values; the SQL function for that is COALESCE:
COALESCE(a.id, b.id)
which returns the first non-NULL value (a.id if it isn't NULL, otherwise b.id). It won't tip you off to different names in the two tables.
I have two tables TABLE_A and TABLE_B having the joined column as the employee number EMPNO.
I want to do a normal left outer join. However, TABLE_B has certain records that are soft-deleted (status='D'), I want these to be included. Just to clarify, TABLE_B could have active records (status= null/a/anything) as well as deleted records, in this case i don't want that employee in my result. If however there are only deleted records of the employee in TABLE_B i want the employee to be included in the result.I hope i'm making my requirement clear. (I could do a lengthy qrslt kind of thingy and get what I want, but I figure there has to be a more optimized way of doing this using the join syntax). Would appreciate any suggestions(even without the join). His newbness is trying the following query without the desired result:
SELECT TABLE_A.EMPNO
FROM TABLE_A
LEFT OUTER JOIN TABLE_B ON TABLE_A.EMPNO = TABLE_B.EMPNO AND TABLE_B.STATUS<>'D'
Much appreciate any help.
Just to clarify -- all records from TABLE_A should appear, unless there are rows in table B with statues other than 'D'?
You'll need at least one non-null column on B (I'll use 'B.ID' as an example, and this approach should work):
SELECT TABLE_A.EMPNO
FROM TABLE_A
LEFT OUTER JOIN TABLE_B ON
(TABLE_A.EMPNO = TABLE_B.EMPNO)
AND (TABLE_B.STATUS <> 'D' OR TABLE_B.STATUS IS NULL)
WHERE
TABLE_B.ID IS NULL
That is, reverse the logic you might think -- join onto TABLE_B only where you have rows that would exclude TABLE_A entries, and then use the IS NULL at the end to exclude those. This means that only those which didn't match (those with no row in TABLE_B, or with only 'D' rows) get included.
An alternative might be
SELECT TABLE_A.EMPNO
FROM TABLE_A
WHERE NOT EXISTS (
SELECT * FROM TABLE_B
WHERE TABLE_B.EMPNO = TABLE_A.EMPNO
AND (TABLE_B.STATUS <> 'D' OR TABLE_B.STATUS IS NULL)
)
The following query will get you the employee records that aren't deleted, or only the employ only has deleted records.
select
a.*
from
table_a a
left join table_b b on
a.empno = b.empno
where
b.status <> 'D'
or (b.status = 'D' and
(select count(distinct status) from table_b where empno = a.empno) = 1)
This is in ANSI SQL, but if I knew your RDBMS, I could give a more specific solution that may be a bit more elegant.
ah crud, this apparently works ><
SELECT TABLE_A.EMPNO
FROM TABLE_A
LEFT OUTER JOIN TABLE_B ON TABLE_A.EMPNO = TABLE_B.EMPNO
where TABLE_B.STATUS<>'D'
If you guys have any extra info to chime in with though, please feel free.
UPDATE:
Saw this question after sometime and thought i'll add more helpful info: This link has good info regarding ANSI syntax - http://www.oracle-base.com/articles/9i/ANSIISOSQLSupport.php
In particular this part from the linked page is informative:
Extra filter conditions can be added to the join to using AND to form a complex join. These are often necessary when filter conditions are required to restrict an outer join. If these filter conditions are placed in the WHERE clause and the outer join returns a NULL value for the filter column the row would be thrown away. if the filter condition is coded as part of the join the situation can be avoided.
SELECT A.*, B.*
FROM
Table_A A
INNER JOIN Table_B B
ON A.EmpNo = B.EmpNo
WHERE
NOT EXISTS (
SELECT *
FROM Table_B X
WHERE
A.EmpNo = X.EmpNo
AND X.Status <> 'D'
)
I think this does the trick. The left join is not needed because you only want to include employees with all (and at least one) deleted rows.
This is how I understand the question. You need to include only those employees for which either of the following is true:
an employee has only (soft-)deleted rows in TABLE_B;
an employee has only non-deleted rows in TABLE_B;
an employee has no rows in TABLE_B at all.
In other words, if an employee has both deleted and non-deleted rows in TABLE_B, omit that employee, otherwise include them.
This is how I think it could be solved:
SELECT DISTINCT a.EMPNO
FROM TABLE_A a
LEFT JOIN TABLE_B b1 ON a.EMPNO = b1.EMPNO
LEFT JOIN TABLE_B b2 ON b1.EMPNO = b2.EMPNO
AND (b1.STATUS = 'D' AND (b2.STATUS <> 'D' OR b2 IS NULL) OR
b2.STATUS = 'D' AND (b1.STATUS <> 'D' OR b1 IS NULL))
WHERE b2.EMPNO /* or whatever non-nullable column there is */ IS NULL
Alternatively, though, you could use grouping:
SELECT a.EMPNO
FROM TABLE_A a
LEFT JOIN TABLE_B b ON a.EMPNO = b1.EMPNO
GROUP BY a.EMPNO
HAVING 0 IN (COUNT(CASE b.STATUS WHEN 'D' THEN 1 ELSE NULL END),
COUNT(CASE b.STATUS WHEN 'D' THEN NULL ELSE 1 END))