I am trying to "short-circuit" an INNER JOIN, if condition isn't met.
What I tried:
I found that if a Left Join is preceded with a False clause on "ON" condition, the LEFT JOIN fails. Hence, I tried to simulate INNER JOIN with LEFT OUTER JOIN and WHERE clause got the execution plan as below:
DECLARE #a nvarchar(4) = 'All'
SELECT A.*
FROM [dbo].[your_table] A
LEFT JOIN [dbo].[your_table_2] B
ON #a <> 'All'
WHERE A.City_Code = CASE WHEN #a <> 'All'
THEN B.City_Code
ELSE A.City_Code END
This will "short-circuit" the left join and it will never occur. Execution plan is below:
But then when I tried to execute the same statement by declaring the variable as 'Al' and not 'All', I saw execution plan was still the same.
I am puzzled if Join happened in the initial step or not?
What I want:
I want to know whether the above approach is correct? Is it really short-circuiting the INNER JOIN?
I basically want the INNER JOIN to happen between the two tables only when variable is not 'All' else it should not JOIN and continue further. I have already tried by using "OR" (to short-circuit) and "IN" (to apply filter) but the performance slows down if you have too many items in IN clause.
Please help me and do tell me if I was wrong anywhere in my approach.
Sample Data:
I should get the INNER JOIN result only when variable <> 'all'
When variable = 'All', I should get table A i.e.
Note: I have simplified this query hence it appears that simple if statement can do. In actual I have 53 parameters that I need to check and run JOINS. Plus result set of one query must be joined with another i.e. I have several other JOIN conditions preceding this :)
Have you tried something like
SELECT A.*
FROM [dbo].[your_table] A
WHERE EXISTS (
SELECT 1
FROM [dbo].[your_table_2] B
WHERE A.City_Code = B.City_Code
)
OR #a = 'All'
Did you try case statement? The CASE or DECODE is usually like an IF-ELSE statement in the SQL.
Related
I'm trying to fetch data from Hana database integrated.
Following is the SQL:-
SELECT alert.UNIQUE_ALERT_ID,
alert.MARK_AS_DELETED,
data.VALUE
FROM "ab"."t-systems.testDB::tables.Alerting" alert
LEFT JOIN
"ab"."t-systems.testDB::tables.AdditionalData" data
ON alert.UNIQUE_ALERT_ID = data.UNIQUE_ALERT_ID
AND data.KEY='batchId'
AND alert.MARK_AS_DELETED != '1';
Problem is I'm getting all the data where Mark_As_Deleted is also 1. The != is not working properly. I tried with <> but problem still persists. I guess something wrong with my Left Join query because when I remove all join and make a simple Select query with same condition as MARK_AS_DELETED != '1', I get proper output but not with Left Join.
I tried re-writing my Left Join query with all possible ways (like moving the condition up & down, etc) but nothing worked.
I would really appreciate if you someone can help me here
When using left join, conditions on the first table should normally go into a where clause.
So I think you want:
SELECT alert.UNIQUE_ALERT_ID, alert.MARK_AS_DELETED, data.VALUE
FROM "ab"."t-systems.testDB::tables.Alerting" alert LEFT JOIN
"ab"."t-systems.testDB::tables.AdditionalData" data
ON alert.UNIQUE_ALERT_ID = data.UNIQUE_ALERT_ID AND
data.KEY = 'batchId'
WHERE alert.MARK_AS_DELETED <> '1'; -- remove the quotes if this is a number
This follows from the definition of a LEFT JOIN. A LEFT JOIN keeps all rows in the first table, regardless of whether the ON clause evaluates to true, false, or NULL.
So, a condition on the first table is ignored. The rule is conditions on the first table go in WHERE and on the second table, in the ON.
I have a view which returns me some nulls values for the columns b.emissor and B.indexador. In case of null, I need to find this values first in table TB_CAD_RF and, if still nulls, I need to query TB_CAD_RF_2.
I try the logic below but its not working. Also tried to think something with case statements but cant figure it out.
Anyone could help me please?
select A.NM_ATIVO, B.EMISSOR, B.INDEXADOR from VW_POSICAO as A
LEFT JOIN
TB_CAD_RF B on A.NM_ATIVO = B.CODIGO
where a.NM_EMISSOR is null
as C LEFT JOIN (
select C.EMISSOR, C.INDEXADOR from TB_CAD_RF_2 as D ON B.NM_ATIVO = C.CODIGO where C.EMISSOR is null)
This pattern:
SELECT
COALESCE( first.choice, second.choice, third.choice) as a
FROM
first
LEFT JOIN second on first.id = second.id
LEFT JOIN third on second.id = third.id
Coalesce returns the first non null passed into it, scanning from left to right
Here is one way. Always join both and coalesce the fields in the order of desired results.
select A.NM_ATIVO,
EMISSOR = COALESCE(A.EMISSOR,B.EMISSOR),
INDEXADOR=COALESCE(A.INDEXADOR,B.INDEXADOR)
from VW_POSICAO A
LEFT JOIN TB_CAD_RF B on A.NM_ATIVO = B.CODIGO
LEFT JOIN TB_CAD_RF_2 D ON A.NM_ATIVO =D.CODIGO
Case when ISNULL((select * from table1) , (select * from table2) ) else select...
ISNULL is like an IIF statement, but if query field returns a null value, it tries the alternate query or you can set an alternate value.
Syntax may be a bit off, haven't written this query in a while, but it should put you on the right path. Google sql ISNULL
Consider below SQL.
SELECT DISTINCT bvc_Order.ID,
bvc_OrderItem.ProductID,
bvc_OrderItem_BundleItem.ProductID
FROM dbo.bvc_OrderItem WITH (nolock)
RIGHT OUTER JOIN dbo.bvc_Order WITH (nolock)
LEFT OUTER JOIN dbo.bvc_User WITH (nolock) ON dbo.bvc_Order.UserID = dbo.bvc_User.ID
LEFT OUTER JOIN dbo.Amazon_Merchants WITH (nolock) ON dbo.bvc_Order.CompanyID = dbo.Amazon_Merchants.ID ON dbo.bvc_OrderItem.OrderID = dbo.bvc_Order.ID
LEFT OUTER JOIN dbo.bvc_OrderItem_BundleItem WITH (nolock) ON dbo.bvc_OrderItem.ID = dbo.bvc_OrderItem_BundleItem.OrderItemID
LEFT OUTER JOIN dbo.bvc_Product WITH (nolock) ON dbo.bvc_OrderItem.ProductID = dbo.bvc_Product.ID
WHERE 1=1
AND (bvc_Order.StatusCode <> 1
AND bvc_Order.StatusCode <> 999)
AND ( bvc_OrderItem.ProductID IN ('28046_00')
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00'))
AND bvc_Order.OrderSource = 56;
The query when I execute against my database, it returns 85 rows. Well, that is not correct.
If I just remove the part "AND bvc_Order.OrderSource = 56" it returns back 5 rows which is really correct.
Strange.....
Another thing, if I remove the part
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00')
it will also return the 5 rows as expected even with bvc_Order.OrderSource filter.
I am not sure why it is adding more rows while I am trying to reduce rows by using filters.
the table bvc_OrderItem_BundleItem doesn't contain any rows for the result order ids or OrderItemIDs
[edit]
Thanks guys, I tried to remove the LEFT/RIGHT Join Mix but Query manager doesn't allows only LEFT, it does add at least one RIGHT join. I updated the SQL to remove extra tables and now we have only three. But same result
SELECT DISTINCT dbo.bvc_Order.ID, dbo.bvc_OrderItem.ProductID, dbo.bvc_OrderItem_BundleItem.ProductID AS Expr1
FROM dbo.bvc_OrderItem
LEFT OUTER JOIN dbo.bvc_OrderItem_BundleItem ON dbo.bvc_OrderItem.ID = dbo.bvc_OrderItem_BundleItem.OrderItemId
RIGHT OUTER JOIN dbo.bvc_Order ON dbo.bvc_OrderItem.OrderID = dbo.bvc_Order.ID
WHERE 1=1
AND (bvc_Order.StatusCode <> 1 AND bvc_Order.StatusCode <> 999)
AND (
bvc_OrderItem.ProductID IN ('28046_00')
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00')
)
AND bvc_Order.OrderSource = 56;
[edit]So far, there is no solution for this. I previously pasted a link in my comment with example data outout for both valid/invalid results with queries. here it is again.
http://sameers.me/SQLIssue.xlsx
One thing to remember here is that ALL left join is not possible. Let me explain further
bvc_Order contains main order record
bvc_ORderItem contains Order Items/Products
bvc_ORderItem_BundleItem contains child products of the product which are available in bvC_OrderItem table.
Now NOT Every product has child products, so bvc_OrderItem_BundleItem may not have any record (and in current scenario, there is really no valid row for the orders in bvC_OrderItem_BundleItem).
In short, in current scenario, there is NO matching row available in bvc_OrderItem_BundleItem table. If I remove that join for now, it is all okay, but in real world, I can't remove that BundleItem table join ofcourse.
thank you
When you say
WHERE bvc_Order.OrderSource = 56
that evaluates to false when bvc_Order.OrderSource is NULL. If the LEFT/RIGHT join failed then it will be NULL. This effectively turns the LEFT/RIGHT join into an inner join.
You probably should write the predicate into the ON clause. An alternative approach, which might not deliver the same results, is:
WHERE (bvc_Order.OrderSource IS NULL OR bvc_Order.OrderSource = 56)
The other predicates have the same problem:
Another thing, if I remove the part OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00') it will also return the 5 rows as expected
When the join fails bvc_OrderItem_BundleItem.ProductID is NULL.
I also would recommend writing queries manually. If I understand you right this query comes from a designer. It's structure is quite confusing. I'm pulling up the most important comment:
Mixing left and right outer joins in a query is just confusing. You should start by rewriting the from clause to only use one type (and I strongly recommend left outer join). – Gordon Linoff
When you have eliminated the impossible, whatever remains, however
improbable, must be the truth? S.H.
It is impossible that an extra AND condition appended to a WHERE clause can ever result in extra rows. That would imply a database engine defect, which I hope I can assume is "impossible". (If not, then I guess it's back to square one).
That fact makes it easier to concentrate on possible reasons:
When you comment out
AND bvc_Order.OrderSource = 56;
then you also comment out the semicolon terminator. Is it possible
that there is text following this query that is affecting it? Try
putting a semicolon at the end of the previous line to make sure.
Depending on the tool you are using to run queries, sometimes when a
query fails to execute, the tool mistakenly shows an old result set.
Make sure your query is executing correctly by adding a dummy column
to the SELECT statement to absolutely prove you are seeing live
results. Which tool are you using?
when you use LEFT outer join it will give all the rows from left table (dbo.bvc_OrderItem) once the your and, or conditions satisfies,
the same thing happens with Right outer join too,
Those conditions (Left join, right join ) may not restrict the rows since rows from one table can be all, another table with some rows only.
check with your join condition
Then check you condition :
(bvc_Order.StatusCode <> 1 AND bvc_Order.StatusCode <> 999)
if any rows satisfying this condition
next check with another condition
[bvc_OrderItem.ProductID IN ('28046_00')
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00')]
Then bvc_Order.OrderSource = 56
compare the result of three queries and check the data in with the conditions and then write your complete query, so that you will understand where the mistake you have done.
Few points to remember
1.And is applied during Virtual join phases
2.Where clause is applied after the final result
3.Left join followed by right join is effectively an inner join in some cases
Lets break your query step by step..
dbo.bvc_OrderItem a1
LEFT OUTER JOIN
dbo.bvc_OrderItem_BundleItem b1
Above output will be a single virtual table (logically) which contains all rows from b1 with matching rows from a1
now below predicates from your and clause will be applied
bvc_OrderItem.ProductID IN ('28046_00')
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00')
which effectively eliminates all rows from bvc_OrderItem_BundleItem even if they have matches and gives result some thing like below if bvc_OrderItem_BundleItem.ProductID IN ('28046_00') is true
bvc_OrderItem bvc_OrderItem_BundleItem
28046 28046
null 1
null 2
null 3
if this condition(bvc_OrderItem.ProductID IN ('28046_00')) is true,then you are asking sql to ignore all rows in bvc_OrderItem ,which effectively means the same result set as above
bvc_OrderItem bvc_OrderItem_BundleItem other columns
28046 28046
null 1
null 2
null 3
next you are doing right outer join with dbo.bvc_Order which may qualifies for the join point I mentioned above
Assume ,you got below result set as output which preserves all of bvc_order table(rough output only for understanding due to lack of actual data)
bvc_OrderItem bvc_OrderItem_BundleItem statuscode ordersource
28046 28046 999 56
null 1 1 57
null 2 100 58
null 3 11 59
Next below AND predicates will be applied
status code <>1 and statuscode<> 999
which means ignore rows which match with bvc_order and has status of 1 ,999 even if they found matching rows
Next you are asking bvc_Order.OrderSource = 56; which means I don't care about other rows,preserve matching rows only for 56 and keep the rest as null
Hope this clarifies on what is happening step by step.A more better way can be provide some test data and show the expected output.
you also can control physical order of joins,you can try below to see if this is what you are trying to do..
SELECT DISTINCT dbo.bvc_Order.ID, dbo.bvc_OrderItem.ProductID, dbo.bvc_OrderItem_BundleItem.ProductID AS Expr1
dbo.bvc_OrderItem
LEFT OUTER JOIN
(
dbo.bvc_OrderItem_BundleItem
RIGHT OUTER JOIN
dbo.bvc_Order
ON dbo.bvc_OrderItem.OrderID = dbo.bvc_OrderItem_BundleItem.OrderItemId
)c
on
dbo.bvc_OrderItem.ID = c.bvc_OrderItem_BundleItem.OrderItemId
WHERE 1=1
AND (bvc_Order.StatusCode <> 1 AND bvc_Order.StatusCode <> 999)
AND (
bvc_OrderItem.ProductID IN ('28046_00')
OR bvc_OrderItem_BundleItem.ProductID IN ('28046_00')
)
AND bvc_Order.OrderSource = 56;
It looks like you are using the Query Designer. I would avoid using this as this can make your queries extremely confusing. Your queries will be much more concise if you are designing them by hand. If you don't completely understand how inner/outer joins work, a great textbook that I used to teach myself SQL is Murach's SQL Server for Developers.
https://www.murach.com/shop/murach-s-sql-server-2012-for-developers-detail
Now, onto the answer.
I've been thinking about how to resolve your problem, and if you are trying to reduce the result set to 5 rows, why are you using multiple outer joins in the first place? I would consider switching the joins to inner joins instead of outer joins if you are looking for a very specific result set. I can't really provide you with a really comprehensive answer without looking at exactly what results you are trying to achieve, but here's a general idea based on what you've provided to all of us:
SELECT DISTINCT dbo.bvc_Order.ID, dbo.bvc_OrderItem.ProductID, dbo.bvc_OrderItem_BundleItem.ProductID AS 'bvc_OrderItem_BundleItem_ProductID'
FROM dbo.bvc_OrderItem
INNER JOIN dbo.bvc_OrderItem_BundleItem ON dbo.bvc_OrderItem.ID = dbo.bvc_OrderItem_BundleItem.OrderItemId
INNER JOIN dbo.bvc_Order ON dbo.bvc_OrderItem.OrderID = dbo.bvc_Order.ID
Start here and then based upon what you are searching for, add where clauses to filter criteria.
Also, your where clause must be rewritten if you use an inner join instead of an outer join:
WHERE 1=1 --not really sure why this is here. This will always be true. Omit this statement to avoid a bad result set.
AND (bvc_Order.StatusCode <> 1 AND bvc_Order.StatusCode <> 999) --this is saying, if the StatusCode is not equal to 1 and not equal to 999, don't include it.
--Revised: Look for Status codes with 1 or 999
--bvc_Order.StatusCode = 1 OR bvc_Order.StatusCode = 999
AND (bvc_OrderItem.ProductID IN ('28046_00') --I would eliminate this unless you are looking to see if this exists in Product ID. You could also accomplish this if you are trying to see if this value is in both tables, change this to:
bvc_OrderItem.ProductID = '28046_00' AND bvc_OrderItem_BundleItem.ProductID = '28046_00')
--if you are trying to see if the order source is 56, use this.
AND bvc_Order.OrderSource = 56;
If you are trying to find out rows that are not included in this result set, then I would use OUTER JOIN as necessary (LEFT preferred). Without more information about what you're looking for in your database, that's the best all of us can do.
bLike #usr writ, the reason of this unexpected (for you) result is, you build query with outer joins, and filter rows after join. If you need filter rows of outer joined tables, you should do this before join.
but probably you try build this:
SELECT DISTINCT o.ID, oi.ProductID, bi.ProductID AS Expr1
FROM dbo.bvc_Order as o
LEFT JOIN dbo.bvc_OrderItem as oi on oi.OrderID = o.ID
LEFT JOIN dbo.bvc_OrderItem_BundleItem as bi ON oi.ID = bi.OrderItemId
WHERE 1=1
AND o.OrderSource = 56;
AND o.StatusCode not in (1, 999)
AND '28046_00' in (oi.ProductID, isnull(bi.ProductID,'_') )
Is this query give results what you need?
if not, try change last condition, for example:
and (bi.ProductID = '28046_00' or bi.ProductID is null and oi.ProductID = '28046_00')
you can also put additional condition in to join conditions, for example:
SELECT DISTINCT o.ID, oi.ProductID, bi.ProductID AS Expr1
FROM dbo.bvc_Order as o
LEFT JOIN dbo.bvc_OrderItem as oi on oi.OrderID = o.ID
LEFT JOIN dbo.bvc_OrderItem_BundleItem as bi ON oi.ID = bi.OrderItemId
and bi.ProductID in ('28046_00') --this join BundleItem only if ...
WHERE 1=1
AND o.OrderSource = 56;
AND o.StatusCode not in (1, 999)
AND (oi.ProductID in ('28046_00') or bi.ProductID is not null)
ah, and if you always need join bvc_Order with bvc_OrderItem then use inner join
If you use a LEFT JOIN and also have a WHERE clause, are all the conditions in the WHERE clause being disregarded if the table that you tried to join does not exist?
In other words, do I have to specifically compare against the id from the LEFT JOIN?
SELECT distinct(watchedItems.id)
FROM globalItems, watchedItems
LEFT JOIN bidGroups ON bidGroups.bidGroupID = watchedItems.bidGroupID
WHERE
watchedItems.aid = globalItems.aid
AND watchedItems.processRunning = 0
(watchedItems.bidGroupID IS NULL
OR (watchedItems.bidGroupID IS NOT NULL AND bidGroups.bidGroupQty > 0))
Could I write instead of the entire last bit just
AND bidGroups.bidGroupQty > 0
and it will not be tested because bidGroups does not exist if the LEFT JOIN fails? I know that without the LEFT JOIN it will definitely test against it all the time, which means if this test fails, the entire statement is not executed. But I want it to be executed in any case (with and without bidGroups.)
If the table doesn't exist your statement won't parse and will result in a SQL exception.
EDIT
I'd write your query this way, for readability:
SELECT distinct(watchedItems.id)
FROM globalItems INNER JOIN
watchedItems ON globalItems.aid = watchedItems.aid LEFT JOIN
bidGroups ON bidGroups.bidGroupID = watchedItems.bidGroupID
WHERE
watchedItems.processRunning = 0
AND (watchedItems.bidGroupID IS NULL
OR (watchedItems.bidGroupID IS NOT NULL
AND bidGroups.bidGroupQty > 0)
);
The answer to whether you need to check watchedItems.bigGroupID IS NOT NULL is no, you do not have to as the join condition already covers that.
First, I wouldn't mix syntax; the , and JOIN mix is a head ache :) Then move the conditions into the LEFT JOIN instead of the WHERE clause?
SELECT
distinct(watchedItems.id)
FROM
globalItems
INNER JOIN
watchedItems
ON watchedItems.aid = globalItems.aid
LEFT JOIN
bidGroups
ON bidGroups.bidGroupID = watchedItems.bidGroupID
AND bidGroups.bidGroupQty > 0
WHERE
watchedItems.processRunning = 0
If left join fails, columns from the missing row all will have value of null, so your test bidGroups.bidGroupQty will always fail. If you want the test to succeed on missing row from left join, the longer logic you have is correct.
The conditions in the where clause are always enforced as written, so you either need to added the null-test logic or move the filter conditions for the outer join to a sub-query. Personally, I'd rewrite your query like so:
SELECT DISTINCT (watcheditems.id)
FROM globalitems
INNER JOIN watcheditems
ON watcheditems.aid = globalitems.aid
LEFT JOIN (SELECT bidgroupid
FROM bidgroups
WHERE bidgroups.bidgroupqty > 0) bg
ON bg.bidgroupid = watcheditems.bidgroupid
WHERE watcheditems.processrunning = 0
The other change I made was to move your inner join into the from clause. Generally, it's a better practice to use the SQL99 standard of putting the joins in the from clause, but whichever method you choose to use, you should be consistent. Putting joins in both the where clause and the from clause is just going to lead to confusion.
I need to retrieve all default settings from the settings table but also grab the character setting if exists for x character.
But this query is only retrieving those settings where character is = 1, not the default settings if the user havent setted anyone.
SELECT `settings`.*, `character_settings`.`value`
FROM (`settings`)
LEFT JOIN `character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
WHERE `character_settings`.`character_id` = '1'
So i should need something like this:
array(
'0' => array('somekey' => 'keyname', 'value' => 'thevalue'),
'1' => array('somekey2' => 'keyname2'),
'2' => array('somekey3' => 'keyname3')
)
Where key 1 and 2 are the default values when key 0 contains the default value with the character value.
The where clause is filtering away rows where the left join doesn't succeed. Move it to the join:
SELECT `settings`.*, `character_settings`.`value`
FROM `settings`
LEFT JOIN
`character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1'
When making OUTER JOINs (ANSI-89 or ANSI-92), filtration location matters because criteria specified in the ON clause is applied before the JOIN is made. Criteria against an OUTER JOINed table provided in the WHERE clause is applied after the JOIN is made. This can produce very different result sets. In comparison, it doesn't matter for INNER JOINs if the criteria is provided in the ON or WHERE clauses -- the result will be the same.
SELECT s.*,
cs.`value`
FROM SETTINGS s
LEFT JOIN CHARACTER_SETTINGS cs ON cs.setting_id = s.id
AND cs.character_id = 1
If I understand your question correctly you want records from the settings database if they don't have a join accross to the character_settings table or if that joined record has character_id = 1.
You should therefore do
SELECT `settings`.*, `character_settings`.`value`
FROM (`settings`)
LEFT OUTER JOIN `character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
WHERE `character_settings`.`character_id` = '1' OR
`character_settings`.character_id is NULL
You might find it easier to understand by using a simple subquery
SELECT `settings`.*, (
SELECT `value` FROM `character_settings`
WHERE `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1') AS cv_value
FROM `settings`
The subquery is allowed to return null, so you don't have to worry about JOIN/WHERE in the main query.
Sometimes, this works faster in MySQL, but compare it against the LEFT JOIN form to see what works best for you.
SELECT s.*, c.value
FROM settings s
LEFT JOIN character_settings c ON c.setting_id = s.id AND c.character_id = '1'
For this problem, as for many others involving non-trivial left joins such as left-joining on inner-joined tables, I find it convenient and somewhat more readable to split the query with a with clause. In your example,
with settings_for_char as (
select setting_id, value from character_settings where character_id = 1
)
select
settings.*,
settings_for_char.value
from
settings
left join settings_for_char on settings_for_char.setting_id = settings.id;
The way I finally understand the top answer is realising (following the Order Of Execution of the SQL query ) that the WHERE clause is applied to the joined table thereby filtering out rows that do not satisfy the WHERE condition from the joined (or output) table. However, moving the WHERE condition to the ON clause applies it to the individual tables prior to joining. This enables the left join to retain rows from the left table even though some column entries of those rows (entries from the right tables) do not satisfy the WHERE condition.
The result is correct based on the SQL statement. Left join returns all values from the right table, and only matching values from the left table.
ID and NAME columns are from the right side table, so are returned.
Score is from the left table, and 30 is returned, as this value relates to Name "Flow". The other Names are NULL as they do not relate to Name "Flow".
The below would return the result you were expecting:
SELECT a.*, b.Score
FROM #Table1 a
LEFT JOIN #Table2 b
ON a.ID = b.T1_ID
WHERE 1=1
AND a.Name = 'Flow'
The SQL applies a filter on the right hand table.