Is there a more elegant way to write the following Microsoft SQL Server 2008 command?
UPDATE TableB
SET TableBField2=0
WHERE TableBID IN(
SELECT TableBID
FROM TableB
JOIN TableA on TableB.TableAID=TableA.TableAID
WHERE TableBField2 < 0
AND TableAField1 = 0
)
In plain speak, what I'm doing is updating a table based on the value of a field in a joined table. I wonder if my use of IN() is considered inefficient.
This should be more efficient:
UPDATE TableB b
SET TableBField2=0
WHERE exists (
SELECT 1
FROM TableA
WHERE b.TableAID=TableA.TableAID
AND b.TableBField2 < 0
AND TableAField1 = 0
)
You can try something like this
UPDATE TableB
SET Field2 = 0
FROM TableB b INNER JOIN
TableA a ON b.TableB.TableAID=a.TableAID
WHERE b.Field2 < 0
AND a.Field1 = 0
Related
I have two tables with one common column, and an identifying value that can be duplicate (several observations of same document).
An example:
TableA:
A_identifier | Value
-------------+-------
1 | A
1 | B
TableB:
B_identifier | A_identifier | Value
-------------+--------------+-------
1 | 1 | A
2 | 1 | B
3 | 1 | B
4 | 1 | C
The above example illustrates the type of situation I am looking for in my data - we have a case in TableA with multiple values, of which some are the same in TableB and some are not. So TableA.Value and TableB.Value represent the same concept.
I want to know for each TableA.A_identifier, how many rows of TableB have different values than TableA.Value. If there was only one observation per A_identifier, this could be solved with a not, but the multiple possible values prevent this.
What I have thought about doing is something like this (which does not work):
select distinct
b.B_identifier, a.A_identifier
from
TableB b
join
TableA a in b.A_identifer = a.A_identifier and b.Value != a.Value
While the query technically works, it returns the wrong result - it counts all the cases where the values in TableA and TableB are different in a given row. However, I want it to only count the values in TableB which are not present at all in TableA for each A_identifier.
I tried replacing the != with not in which is what I would do for a static parameter. This syntax is not supported.
I hope my question makes sense, and that somebody can help. Thank you in advance.
Try this query if it works for you,
SELECT COUNT(b.A_identifier)
FROM TableB b
LEFT JOIN TableA a
ON b.A_identifier = a.A_identifier
AND b.Value = a.Value
WHERE a.A_identifier IS NULL -- filters out inexisting value
AND EXISTS (SELECT 1
FROM TableA c
WHERE b.A_identifier = c.A_identifier) -- shows only A_identifier
-- that is present in TableA
However, if you want to get the count for each Value
SELECT b.A_identifier, b.Value, TOTAL_COUNT = COUNT(b.A_identifier)
FROM TableB b
LEFT JOIN TableA a
ON b.A_identifier = a.A_identifier
AND b.Value = a.Value
WHERE a.A_identifier IS NULL
AND EXISTS (SELECT 1
FROM TableA c
WHERE b.A_identifier = c.A_identifier)
GROUP BY b.A_identifier, b.Value
Use NOT EXISTS
select t1.A_identifier, count(t2.value)
from TableA t1
left join TableB t2 on t1.A_identifier = t2.A_identifier and
NOT EXISTS (
select 1
from TableA t3
where t3.A_identifier = t2.A_identifier and
t3.Value = t2.Value
)
group by t1.A_identifier
How about the following SQL?
select distinct TableA.A_identifier,
(select count(*) from TableB
where TableB.A_identifier = TableA.A_identifier
and not exists(
select * from TableA where A_identifier = TableB.A_identifier
and Value = TableB.Value)
)
as TableB_Rows
from TableA
I have 2 tables say A and B, and I want to do a join on them.
Table A will always have records in it.
When table B has rows in it, I want the query to turn all the rows in which table A and table B matches. (i.e. behave like inner join)
However, if table B is empty, I'd like to return everything from table A.
Is this possible to do in 1 query?
Thanks.
Yes, for results like this, use LEFT JOIN.
Basically what INNER JOIN does is it only returns row where it has atleast one match on the other table. The LEFT JOIN, on the other hand, returns all records on the left hand side table whether it has not match on the other table.
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
I came across the same question and, as it was never answered, I post a solution given to this problem somewhere else in case it helps someone in the future.
See the source.
select *
from TableA as a
left join TableB as b
on b.A_Id = a.A_Id
where
b.A_Id is not null or
not exists (select top 1 A_Id from TableB)
Here is another one, but you need to add one "null" row to table B if it's empty
-- In case B is empty
Insert into TableB (col1,col2) values (null,null)
select *
from TableA as a inner join TableB as b
on
b.A_Id = a.A_Id
or b.A_Id is null
I would use an if-else block to solve it like below:
if (select count(*) from tableB) > 0
begin
Select * from TableA a Inner Join TableB b on a.ID = b.A_ID
end
else
begin
Select * from TableA
end
Try This
SELECT t1.* FROM table1 AS t1 INNER JOIN table2 AS t2 ON t1.something = t2.someotherthing UNION SELECT * FROM table1 WHERE something = somethingelse;
This is solution:
CREATE TABLE MyData(Id INT, Something VARCHAR(10), OwnerId INT);
CREATE TABLE OwnerFilter(OwnerId INT);
SELECT *
FROM
(SELECT NULL AS Gr) AS Dummy
LEFT JOIN OwnerFilter F ON (1 = 1)
JOIN MyData D ON (F.OwnerId IS NULL OR D.OwnerId = F.OwnerId);
Link to sqlfiddle: http://sqlfiddle.com/#!6/0f9d9/7
I did the following:
DECLARE #TableB TABLE (id INT)
-- INSERT INTO #TableB
-- VALUES (some ids to filter by)
SELECT TOP 10 *
FROM [TableA] A
LEFT JOIN #TableB B
ON A.ID = B.id
WHERE B.id IS NOT NULL
OR iif(exists(SELECT *
FROM TableB), 1, 0) = 0
Now:
If TableB is empty (leave the commented lines commented) you'll get the top 10.
If TableB has some ids in it, you'll only join by those.
I do not know how efficient this is. Comments are welcome.
Maybe use a CTE
;WITH ctetable(
Select * from TableA
)
IF(EXISTS(SELECT 1 FROM TableB))
BEGIN
Select * from ctetable
Inner join TableB
END
ELSE
BEGIN
Select * from ctetable
END
or dynamic SQL
DECLARE #Query NVARCHAR(max);
SET #QUERY = 'Select * FROM TableA';
IF(EXISTS(SELECT 1 FROM TableB))
BEGIN
SET #QUERY = CONCAT(#QUERY,' INNER JOIN TableB');
END
EXEC sp_executesql #Query
I have found lots of posts on coniditonal filtering in the where clause, but they all seem to be based off of using the same value, such as:
WHERE (o.OrderID = #orderid OR #orderid IS NULL)
I need to do something slightly different, I need to remove a filter and its value completely base on another value, so something like:
select *
from tableA
where 1 = 1
case when a = 1 then
and b in (select b from tableB)
else
-- do nothing
end
I know that the above is not allowed, and I am just writing as an example of what I am trying to do. does Anyone have any idea of a good way to do this? I know i could use if statements and duplicate the query, but it is a large one, and i am trying to avoid that.
Thanks
SELECT *
FROM tableA
WHERE a <> 1
OR (a = 1 AND EXISTS(SELECT b from TableB WHERE tableA.b = TableB.b))
You could also write this as:
SELECT tableA.*
FROM tableA
LEFT JOIN tableB
ON tableA.b = tableB.b
WHERE tableA.a <> 1
OR (tableA.a = 1 AND tableB.b IS NOT NULL)
"Correcting" your WHERE clause:
select *
from tableA
where 'T' = case
when a = 1 then case
when b in (select b from tableB) then 'T'
end
else 'T'
end;
I created a table from a CSV file. Although the table has all the data we could ever need for this project, the resulting table is not normalized. My task is to clean and normalize this table.
Given a field value Value1 from TableA, how do I lookup that value in TableB and place the PK from TableB in a FK column in TableA?
Same as Question 1 exception I need to lookup multiple columns. Given field values Value1 and Value2 from TableA, how do I lookup that combination in TableB and place the PK From TableB in a FK column in TableA?
This should work for #1:
UPDATE TableA
SET FKColumn = b.PKColumn
FROM TableA as a
INNER JOIN TableB as b
ON a.Value1 = b.Value1
For #2:
UPDATE TableA
SET FKColumn = b.PKColumn
FROM TableA as a
INNER JOIN TableB as b
ON a.Value1 = b.Value1 AND a.Value2 = b.Value2
UPDATE TableA SET FKColumn = TableB.PKColumn
FROM TableB
WHERE TableA.Value1 = TableB.Value1
UPDATE TableA SET FKColumn = TableB.PKColumn
FROM TableB
WHERE TableA.Value1 = TableB.Value1 AND TableA.Value2 = TableB.Value2
UPDATE TableA a
SET a.fk_col = (select b.pk_col
from TableB b
where b.value = a.value);
And
UPDATE TableA a
SET a.fk_col = (select b.pk_col
from TableB b
where b.value = a.value1
and b.value = a.value2);
Logically, it should be something like this:
UPDATE TableA
SET FK_col =
(SELECT PK_col
FROM TableB
WHERE TableB.TableA_field = TableA.field)
WHERE <your filter criteria on TableA>
However, at least in MySQL, you can't directly reference TableA in sub-queries like this in some circumstances, but this can be worked around in different ways depending upon the circumstances. I'm not sure if the same applies to SQL Server or not - never touched it.
Edit: I think the other answers posted in the meantime are probably better than mine! ;)
I can do this with linq easy but i got a situation where i have to create a stored procedure to return true or false based on 2 fields(minrange,maxrange) in table B. So, the goal is given an id from table A, i select the range value from table A and compare this value to the 2 ranges in table B. If the value is within range(minrange,maxrange) return true. Thanks.
I'm assuming you have a field that allows you to join records from Table A to Table B. I'll call it "CategoryID". Try this:
SELECT
CASE WHEN TableA.Value BETWEEN TableB.MinValue AND TableB.MaxValue
THEN 1 ELSE 0 END
FROM TableA
INNER JOIN TableB ON TableA.CategoryID = TableB.CategoryID
WHERE TableA.ID = "TheID"
Good luck!
-Michael
Without knowing specifics (as to foreign keys), this syntax should work.
SELECT
CAST((CASE
WHEN tableAValue < tableB.maxRange and tableAValue > tableB.minRange
THEN 1
ELSE
0
END) AS BIT)
FROM TableA
INNER JOIN TableB
ON TableA.ID = TableB.TableAID
WHERE TableA.ID = #yourID