I have two tables -> tb1 and tb2.
I am performing left join operation on these tables using ID column and also i have one more condition such as one column is not equal to other column .
Below is sample code
select * from tb1 LEFT JOIN tb2 ON tb1.id=tb2.id AND tb1.pid!=tb2.pid;
I am able to get results from above query.
But i need to know is there any alternate ways to get same result using sql.?
The actually SQL standard uses <> instead of !=.
select * from tb1 LEFT JOIN tb2 ON tb1.id=tb2.id AND tb1.pid<>tb2.pid;
It seems to you not equal not working because of your join and join condition.
if we create two tables and create like your query
create table t1(id int,pid int);
create table t2 (id int,pid int );
insert into t1 values(1,2),(2,3),(3,4);
insert into t2 values(1,2),(2,3),(3,4);
select t1.* from t1 left join
t2 on t1.id=t2.id and
t1.pid!=t2.pid
order by t1.id
id pid
1 2
2 3
3 4
It returns all the values of 1st table, because LEFT JOIN returns all records from the left table (table1), and the matched records from the right table (table2). The result is NULL from the right side, if there is no match.
But if you put inner join in the same it will not return any row. so i think problem is not in the "not equal operator"
Related
I have 3 tables of accounts that all contain the same fields. Table1 contains all accounts while Table2 and Table3 contain subsets of the accounts. I'm trying to select records in Table1 that do no exist in Table2 or Table3.
Let's say the table layout is like this and is the same for all 3 tables:
|AcctNum|Name|State|
I know how to do this if it was just Table1 and Table2, using a left join and Is Null, but the 3rd table is throwing me. Is this possible to do in one query? Can you combine left joins? I should point out I'm using Access 2010.
Yes you can combine left joins and with the odd syntax Access uses the query should look like this:
SELECT T1.AcctNum
FROM (Table1 AS T1 LEFT JOIN Table2 AS T2 ON T1.AcctNum = T2.AcctNum)
LEFT JOIN Table3 AS T3 ON T1.AcctNum = T3.AcctNum
WHERE (((T2.AcctNum) Is Null) AND ((T3.AcctNum) Is Null));
You can use Access to create a view called TableCombined that is a union of both Table2 and Table3.
At that point, you can use your left join and Is Null query and join TableCombined to Table1.
Hope this helps!
You can also do a NOT EXISTS statement which makes sense logically for what you are trying to achieve.
For example:
SELECT ACCTNUM
FROM TABLE1
WHERE NOT EXISTS (SELECT TABLE2.ACCTNUM FROM TABLE2 INNER JOIN TABLE3 WHERE TABLE2.ACCTNUM IS NULL AND TABLE3.ACCTNUM IS NULL)
I have been working on this problem for 3 months now and gave up once or twice. Yes, I am a novice. I created 3 tables with data. Table 1 has a letter and number. Table 2 has a name, letter and number. Table 3 has the end result. I want to compare the T1 and T2. If the name and number in T1 matches a name and number in table 2. I want the result to in T3 to include name, letter and number. This is what I have so far but it is not working.
SELECT * FROM T1 and SELECT * FROM T2
WHEN
TABLE T1(letter) && TABLE T2(letter)
AND
TABLE T1(number) && TABLE T2(letter)
INSERT INTO TABLE T3 (name,letter,number)
What you need is to do an inner join of the first and second tables based on the attributes name and letter.
SELECT T2.name, T2.letter, T2.number
FROM T1
INNER JOIN T2
ON T1.letter=T2.letter AND T1.number=T2.number;
For more details, you can refer http://www.w3schools.com/sql/sql_join.asp
To expand upon Dinesh's answer,
You'll need an inner join for this. Inner joins gives you rows that match the columns in both tables you've specified.
You can then combine it into an insert statement to put it into your T3 table. So this is one complete SQL statement:
INSERT INTO T3
SELECT T2.name, T2.letter, T2.number
FROM T2
INNER JOIN T1
ON T2.letter = T1.letter
AND T2.number = T1.number;
As a side note, there's also left joins and right joins (and heaps more). Think of Left, Inner, Right joins as two circles in a venn diagram.
I'm a newbie here and hoping someone can help with this sql. I've created two tables, one of which holds EVERY record, another which contains the records that I DON'T want in my table.
I tried joining them in the way I researched that is supposed to work, to include only records where they ARE NOT In the second table, but I'm getting an error.
The SQL is:
Create table t3 as
(Select * from t1
Left Outer join t2
on (t1.ID = t2.Orig_ID and t1.ID_Line = t2.Orig_ID_Line)
Where t2.Orig_ID is null
and t2.Orig_ID_Line is null)
This should be simple. However, i'm getting an error that says "Duplicate column name in Orig_ID"
HELP!
Thanks.
You were very close with your original statement, but forgot to limit the columns to those from t1, so you had twice as many columns as intended. Try:
CREATE TABLE t3 AS
(SELECT t1.* FROM t1 -- Key change * -> t1.*
LEFT OUTER JOIN t2
ON (t1.ID = t2.Orig_ID AND t1.ID_Line = t2.Orig_ID_Line)
WHERE t2.Orig_ID IS NULL
AND t2.Orig_ID_Line IS NULL)
Try this
Create table t3 as
select * from t1 where (t1.ID, t1.ID_Line) not in ( select t2.ID, t2.Orig_ID_Line from t2 where t2.ID is not null and t2.Orig_ID_Line is not null )
You get duplicate column name error, because you join and select both fields in both tables. So same column names return from the query and table can not have same column names. What you need is to select columns only in t1 table
select t1.* ......
But you do not need join operation. What you need is simple. Using "not in" operator is what you need. Have a look at an sql tutorial for in/not in operators.
I have one table that contains lots of data and I want to select everything from this one.
Another table contains different statuscodes ( fields ID and text ), and I want to join this table into the first one so i get something like
All data from first table id1,text2,id2,text2 or id1,id2,text1,text2 from the second table.
USe LEFT OUTER JOIN
Select T1.*,T2.ID,T2.Text
from firstTable t1
LEFT OUTER JOIN SecondTable T2
on T1.<col>=T2.<col>
You can use join like this whether it may be left/right/inner join
SELECT t1.*,t2.id,t2.text
FROM table1 t1
LEFT JOIN table2 t2
ON t2.column_name=t1.column_name
For example, there are two tables:
create table Table1 (id int, Name varchar (10))
create table Table2 (id int, Name varchar (10))
Table1 data as follows:
Id Name
-------------
1 A
2 B
Table2 data as follows:
Id Name
-------------
1 A
2 B
3 C
If I execute both below mentioned SQL statements, both outputs will be the same:
select *
from Table1
left join Table2 on Table1.id = Table2.id
select *
from Table2
right join Table1 on Table1.id = Table2.id
Please explain the difference between left and right join in the above SQL statements.
Select * from Table1 left join Table2 ...
and
Select * from Table2 right join Table1 ...
are indeed completely interchangeable. Try however Table2 left join Table1 (or its identical pair, Table1 right join Table2) to see a difference. This query should give you more rows, since Table2 contains a row with an id which is not present in Table1.
Table from which you are taking data is 'LEFT'.
Table you are joining is 'RIGHT'.
LEFT JOIN: Take all items from left table AND (only) matching items from right table.
RIGHT JOIN: Take all items from right table AND (only) matching items from left table.
So:
Select * from Table1 left join Table2 on Table1.id = Table2.id
gives:
Id Name
-------------
1 A
2 B
but:
Select * from Table1 right join Table2 on Table1.id = Table2.id
gives:
Id Name
-------------
1 A
2 B
3 C
you were right joining table with less rows on table with more rows
AND
again, left joining table with less rows on table with more rows
Try:
If Table1.Rows.Count > Table2.Rows.Count Then
' Left Join
Else
' Right Join
End If
You seem to be asking, "If I can rewrite a RIGHT OUTER JOIN using LEFT OUTER JOIN syntax then why have a RIGHT OUTER JOIN syntax at all?" I think the answer to this question is, because the designers of the language didn't want to place such a restriction on users (and I think they would have been criticized if they did), which would force users to change the order of tables in the FROM clause in some circumstances when merely changing the join type.
select fields
from tableA --left
left join tableB --right
on tableA.key = tableB.key
The table in the from in this example tableA, is on the left side of relation.
tableA <- tableB
[left]------[right]
So if you want to take all rows from the left table (tableA), even if there are no matches in the right table (tableB), you'll use the "left join".
And if you want to take all rows from the right table (tableB), even if there are no matches in the left table (tableA), you will use the right join.
Thus, the following query is equivalent to that used above.
select fields
from tableB
right join tableA on tableB.key = tableA.key
Your two statements are equivalent.
Most people only use LEFT JOIN since it seems more intuitive, and it's universal syntax - I don't think all RDBMS support RIGHT JOIN.
I feel we may require AND condition in where clause of last figure of Outer Excluding JOIN so that we get the desired result of A Union B Minus A Interaction B.
I feel query needs to be updated to
SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL AND B.Key IS NULL
If we use OR , then we will get all the results of A Union B
select *
from Table1
left join Table2 on Table1.id = Table2.id
In the first query Left join compares left-sided table table1 to right-sided table table2.
In Which all the properties of table1 will be shown, whereas in table2 only those properties will be shown in which condition get true.
select *
from Table2
right join Table1 on Table1.id = Table2.id
In the first query Right join compares right-sided table table1 to left-sided table table2.
In Which all the properties of table1 will be shown, whereas in table2 only those properties will be shown in which condition get true.
Both queries will give the same result because the order of table declaration in query are different like you are declaring table1 and table2 in left and right respectively in first left join query, and also declaring table1 and table2 in right and left respectively in second right join query.
This is the reason why you are getting the same result in both queries. So if you want different result then execute this two queries respectively,
select *
from Table1
left join Table2 on Table1.id = Table2.id
select *
from Table1
right join Table2 on Table1.id = Table2.id
Select * from Table1 t1 Left Join Table2 t2 on t1.id=t2.id
By definition: Left Join selects all columns mentioned with the "select" keyword from Table 1 and the columns from Table 2 which matches the criteria after the "on" keyword.
Similarly,By definition: Right Join selects all columns mentioned with the "select" keyword from Table 2 and the columns from Table 1 which matches the criteria after the "on" keyword.
Referring to your question, id's in both the tables are compared with all the columns needed to be thrown in the output. So, ids 1 and 2 are common in the both the tables and as a result in the result you will have four columns with id and name columns from first and second tables in order.
*select *
from Table1
left join Table2 on Table1.id = Table2.id
The above expression,it takes all the records (rows) from table 1 and columns, with matching id's from table 1 and table 2, from table 2.
select *
from Table2
right join Table1 on Table1.id = Table2.id**
Similarly from the above expression,it takes all the records (rows) from table 1 and columns, with matching id's from table 1 and table 2, from table 2. (remember, this is a right join so all the columns from table2 and not from table1 will be considered).