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I am learning SQL and am trying to learn JOINs this week.
I have gotten to the level where I can do three table joins, similar to a lot of examples I've seen. I'm still trying to figure out the tiny details of how things work. All the examples I've seen...
Started by MedicineMan on
, 9 posts
by 9 people.
Answer Snippets (Read the full thread at stackoverflow):
The same general logic applies when selecting the join type when you have multiples as with single join the query easier for the....
It just depends on the data you are querying and what you are trying to follow .
An outer join in them.
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What is the difference between an inner join and outer join? What's the precise meaning of these two kinds of joins?
Started by freenight on
, 10 posts
by 10 people.
Answer Snippets (Read the full thread at stackoverflow):
INNER JOIN returns rows that exist in both tables
OUTER JOIN returns all rows that exist in either excellent:
A Visual Explanation of SQL Joins
INNER JOIN
LEFT OUTER JOIN
Marc
Wikipedia to the rescue:
Inner Joins....
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Duplicate: What is the difference between Left, Right, Outer and Inner Joins?
INNER and LEFT OUTER join help
Just a simple question, I know left join is a type of inner join, but when I'm querying something there's a difference. I don't know what it is...
Started by Malfist on
, 13 posts
by 13 people.
Answer Snippets (Read the full thread at stackoverflow):
An inner join only returns one row per match , so some rows of the left table could....
A left join ensures at least one row is returned it uses NULL for the right-table's fields).
Left join is actually an alias for an outer join.
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What is the difference between left join and left outer join?
Started by KG Sosa on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Also note that the entire type....
As per the documentation: FROM (Transact-SQL) :
<join_type> ::= [ { INNER | { { LEFT | RIGHT | FULL } [ OUTER ] } } [ <join_hint> ] ] JOIN
The keyword OUTER.
They are equivalent.
Nothing.
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What are the performance gains/losses between hash joins and merge joins, specifically in Oracle RDBMS?
Started by Raegx on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
IF you have two tables (or covering indexes) that have their ordering the same such as a primary key and an index of ... .
Merge join is the best possible as it exploits the ordering, resulting in a single pass down the tables to do the join.
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What are the advantages, if any, of explicitly doing a HASH JOIN over a regular JOIN (wherein SQL Server will decide the best JOIN strategy)? Eg:
select pd.* from profiledata pd inner hash join profiledatavalue val on val.profiledataid=pd.id
In the simplistic...
Started by Garrett on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
Hence, the rationale behind those commands is to let the user specify the optimal join strategy and scale better than any other join and are great at maximizing throughput in data warehouses JOIN hint will becomes obsolete and prevents....
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Are there any performance drawbacks in SQL to joining a table on a char (or varchar) value, as opposed to say joining on an integer value?
Started by Aaron F. on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
An integer....
No, as long as the datatypes are the same between the tables that you join of the join column.
What can make a difference is:
- If datatypes in your join-condition than in the other column.
No there is not (in Oracle).
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I've got the following request :
select * from tbA A, tbB B, tbC C, tbD D where A.ID=B.ID and B.ID2= C.ID2 and A.ID=D.ID and C.ID3=D.ID3 and B.ID4=D.ID4 and A.Foo='Foo'
I've heard several times that this join syntax is depreciated, and that I should use...
Started by Brann on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
I find join syntax much easier to understand
select * from tbA A inner join tbB B on a.id = b.id inner join tbC C on b.id2 = c.id2 inner join tbD D on a.id = d.id and c.id3 = d.id3 and b.id4 = d.id4 complicated join ....
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Hi all,
Say we have the following tables t1 and t2:
t1: id | column_1 1 | 1 2 | 2 t2: id | column_2 2 | 2 3 | 3
and we want to find the following result:
id | column_1 | column_2 1 | 1 | 2 | 2 | 2 3 | | 3
This basically is the union of a right join with...
Started by Pierre Spring on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Outer join t1 on a.id = t1.id left outer join t2 on a.id = t2.id
Haven't tried this myself, but this might work:
SELECT t1.id, t1.column_1, t2.column_2, t2a.column_2 FROM t1 LEFT JOIN t2 ON t1.id = t2.id RIGHT JOIN t2 AS ....
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Both these joins will give me the same results:
SELECT * FROM table JOIN otherTable ON table.ID = otherTable.FK
vs
SELECT * FROM table INNER JOIN otherTable ON table.ID = otherTable.FK
Is there any difference between the statements in performance or otherwise...
Started by driis on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
However for some reason I always use "OUTER" as in LEFT OUTER JOIN and never....
LEFT keyword that makes the JOIN an "OUTER" JOIN.
JOIN can be a bit more clear to read, especially if your query has other join types (e.g.
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