Can anyone explain about join?

Question Posted / thilakar

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Can anyone explain about join?..

Answer / sekar

SQL JOIN:

type of join

1.cross join
Ans :
cross join not support where clause.
The size of cartesian product result set is number
of row in first table multiplied by number of row in second
table.

2.inner join
Ans: Inner join is used to retrive the matching record
first and second table.

3.self join
Ans:Self join is used to retrive matching record in same
table.

4.right outer join
Ans:right outer join is used to return the all the value of
second table and plus matching record(innerjoin) of both
table.

5.left outer join
Ans:left outer join is used to return the all the value of
first table and plus matching record(innerjoin) of both
table.

6 full outer join

Example:
<?php
$con = mysql_connect("localhost","root","") or die ("could
not connet".mysql_error());
$db = mysql_select_db("sekar",$con) or die ("could not
connet".mysql_error());
//$sql = mysql_query("create table emp2(eno int(4) not null
auto_increment primary key, ename varchar(20), sal int
(10))") or die ("could not connet".mysql_error());
//$record = mysql_query("insert into std2(sno, sname, mark)
values (4, 'krish', 100)") or die("could not
add".mysql_error());
//$record = mysql_query("insert into emp2(eno, ename, sal)
values (4, 'kanna', 10000)") or die("could not
add".mysql_error());
/*cross join
$query = "select * from std2, emp2";
$query = "select s.sname, s.mark, e.ename,e.sal from std2
s,emp2 e";
*/
/*inner join
$query = "select s.sname, s.mark, e.ename,e.sal from std2 s
inner join emp2 e on(s.sname= e.ename)";
*/
/*self join
$query = "select s.sname, s.mark, e.sname from std2 s join
std2 e on(s.sname= e.sname)";
*/
/*Right outer join
$query = "select s.sname, s.mark, e.ename,e.sal from std2 s
left outer join emp2 e on(s.sname= e.ename)";
*/
/*Right outer join
$query = "select s.sname, s.mark, e.ename,e.sal from std2 s
right outer join emp2 e on(s.sname= e.ename)";
*/
//full outer join
$query = "select s.sname, s.mark, e.ename,e.sal from std2 s
join emp2 e on(s.sname= e.ename)";

$result= mysql_query($query) or die("could not
select".mysql_error());
echo "<table border='1' cellpadding='0' cellspacing='0'
width='700'>";
while($rec = mysql_fetch_array($result))
{
$sno = $rec[sno];
$sname = $rec[sname];
$mark = $rec[mark];
$eno = $rec[eno];
$ename = $rec[ename];
$sal = $rec[sal];
echo "<tr><td>$sno</td><td>$sname</td><td>$mark</td>
<td>$eno</td><td>$ename</td><td>$sal</td></tr>";
}
echo "</table>";
echo "sucess"
?>

Is This Answer Correct ?

13 Yes

1 No

Can anyone explain about join?..

Answer / vipin gurjar

join :- when we want to fetch the records from more then
two tables which r interlinked then we use the joins to
fetch a proper result. Joins query depends on that what
type of result we want.

there are many types of join like
1)Inner join 2)left join 3) Outer Join 4)Simple Join

example of these are as follows:-

Is This Answer Correct ?

8 Yes

1 No

Can anyone explain about join?..

Answer / guest

join is basically use to join b/w tables;

Is This Answer Correct ?

2 Yes

0 No

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