I know that inner join operation is only supported from ORMlite version 4.42 and above. Does there exist a way to replace inner join operation functionality in previous ormlite versions -- without doing separate querys?
You can always do your own joins using raw queries:
http://ormlite.com/docs/raw-queries
But otherwise the answer is no.
Related
I'm recently studying SQL Server. I read a book and it says that merge join requires at least one equal sign(=) on ON clause in SQL Server.
So, I tried this query below and I found that the error occurs.
SELECT *
FROM TABLE_1 AS T1
INNER MERGE JOIN TABLE_2 AS T2
ON T1.COL_1 > T2.COL_2
Error Message:
Msg 8622, Level 16, State 1, Line 6 Query processor could not produce
a query plan because of the hints defined in this query. Resubmit the
query without specifying any hints and without using SET FORCEPLAN.
And this book also says this can be done in case of Full Outer Join.
So I tried this query below and found it committed successfully with no errors.
SELECT *
FROM TABLE_1 AS T1
FULL OUTER MERGE JOIN TABLE_2 AS T2
ON T1.COL_1 > T2.COL_2
I tried to search for the reason but I couldn't find any explanation about this.
Can anyone tell me why SQL Server doesn't allow merge join without an equality operator unless it's full outer join?
Thank you for reading my question
You used Inner Merge Join. Merge clause is a join hint that tells sql engine to work more efficient.
Merge joins have the fastest algorithm since each row only needs to be read once from the source inputs. Also, optimizations occurring in other join operators can give those operators better performance under certain conditions.
if you must use '>' operator, use regular Inner Join, like this.
SELECT *
FROM TABLE_1 AS T1
INNER JOIN TABLE_2 AS T2
ON T1.COL_1 > T2.COL_2
I'm rewriting a bunch of old, badly written Oracle queries against a new(-er) Sql Server 2008 environment. They use old-school Oracle join syntax like
select <whatever>
from Table1, Table2, Table3
where Table1.T1ID = Table2.T2ID -- old Oracle inner join
and Table2.T3ID = Table3.T3ID (+) -- old Oracle left join (I think)
Except a lot more complicated. There's a lot of mixed joins and a lot of nesting and a lot of views piled on views going on in these things. It's not pretty. The data is disparate between the two servers too, making testing a chore.
I figured the easiest way to replicate would be to make the queries look as similar as possible in Sql Server (ie, using the same style of join), and then do a massive clean-up job after once I'm confident they're both definitely doing the same thing & I don't have a join in the wrong place somewhere (and yes, I have compatibility mode temporarily set to support old joins).
I know the 'old' syntax for an inner join in T-Sql is
select <whatever>
from T1, T2
where T1.ID = T2.ID
but what is the 'old' syntax for a left outer join or a right outer join?
From the documentation on TechNet (on SQL Server 2000, so be aware this might not be supported any more!), you need to use *= instead of the (+) as Oracle does:
select <whatever>
from T1, T2
where T1.ID *= T2.ID
THe below 2 queries performs the same operation, but wondering which would be the fastest and most preferable?
NUM is the primary key on table1 & table2...
select *
from table1 tb1,
table2 tb2
where tb1.num = tb2.num
select *
from table1 tb1
inner join
table2 tb2
on tb1.num = tb2.num
They are the same query. The first is an older alternate syntax, but they both mean do an inner join.
You should avoid using the older syntax. It's not just readability, but as you build more complex queries, there are things that you simply can't do with the old syntax. Additionally, the old syntax is going through a slow process of being phased out, with the equivalent outer join syntax marked as deprecated in most products, and iirc dropped already in at least one.
The 2 SQL statements are equivalent. You can look at the execution plan to confirm. As a rule, given 2 SQL statements which affect/return the same rows in the same way, the server is free to execute them the same way.
They're equivalent queries - both are inner joins, but the first uses an older, implicit join syntax. Your database should execute them in exactly the same way.
If you're unsure, you could always use the SQL Management Studio to view and compare the execution plans of both queries.
The first example is what I have seen referred to as an Oracle Join. As mentioned already there appears to be little performance difference. I prefer the second example from a readability standpoint because it separates join conditions from filter conditions.
I am using SQL Server 2008 R2. I want to join tables but always get the error
The multi-part identifier could not be bound
I have 3 tables Drivers, Request and Journey. I have driver_id foreign key in Journey. How can I join these tables to get details of all three tables??
Select driver.driver_name
from Drivers,
Journey
where driver.id = journey.id
and driver.id=1;
This error usually occurs when an alias is used when referencing a column in a SELECT statement and the alias used is not defined anywhere in the FROM clause of the SELECT statement.
For more details visit here
You only seem to be joining two of your three tables - correct?
The proper, ANSI SQL-92 standard-compliant way to do this would be:
SELECT
driver.driver_name
FROM
Drivers
INNER JOIN
Journey ON driver.id = journey.id
WHERE
driver.id = 1;
This is using the ANSI standard (in place since 1992 - more than 20 years now!) JOIN syntax of INNER JOIN (there's also LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL JOIN and a few more) instead of just comma-separating a list of tables in the FROM clause.
See Aaron Bertrand's excellent blog post Bad habits to kick : using old-style JOINs on that topic, too.
driver+s
Select Drivers.driver_name
from Drivers,
Journey
where Drivers.id = journey.id
and Drivers.id=1;
I am trying to understand how JOINS work on SQL Server 2000 and 2005 SPECIFICALLY.
In general, I understand how inner joins, left joins and right joins work.
However, all the articles that I've read, explain it with examples, but are not specific to any RDBMS. So now I am confused to the different types of joins, which are just synonyms of other joins, and which are actually different.
For e.g.,
Is LEFT OUTER JOIN the same as LEFT JOIN?
Is RIGHT OUTER JOIN the same as RIGHT JOIN?
Does SQL Server support FULL OUTER JOIN, CROSS JOIN? What are the different types of joins, and their synonyms. All these keywords are confusing me.
Yes, SQL Server supports FULL OUTER JOIN and CROSS JOIN.
And yes again, LEFT JOIN is a synonym for LEFT OUTER JOIN. The same applies to RIGHT JOIN.
In addition, FULL JOIN is a also a synonym for FULL OUTER JOIN.
You might be interested in checking out the following article by Jeff Atwood:
Coding Horror: A Visual Explanation of SQL Joins
Duplicate of : Difference between JOIN and OUTER JOIN in MySQL
There is no diffrence between Right Join and Right outer Join both are same. i.e Left Join and Left Outer Join both are same.
This will give you clear idea :
Visual Representation of SQL Joins