7/23/2019 Syntax Join

1/3

The most frequently used and important of the joins is the INNER JOIN. They are also referred

to as an EQUIJOIN.

The INNER JOIN creates a new result tale y cominin! column "alues of two tales #tale$

and tale%& ased upon the join'predicate. The query compares each row of tale$ with each row

of tale% to find all pairs of rows which satisfy the join'predicate. (hen the join'predicate is

satisfied) column "alues for each matched pair of rows of * and + are comined into a result

row.

Syntax:

The asic synta, of INNER JOINis as follows-

SELECT table1.column1, table2.column2...

FROM table1INNER JOIN table2

ON table1.common_field table2.common_field!

2.

The Q/ LEFT JOINreturns all rows from the left tale) e"en if there are no matches in the

ri!ht tale. This means that if the ON clause matches 0 #1ero& records in ri!ht tale) the join will

still return a row in the result) ut with NU// in each column from ri!ht tale.

This means that a left join returns all the "alues from the left tale) plus matched "alues from the

ri!ht tale or NU// in case of no matchin! join predicate.

Syntax:

The asic synta, of LEFT JOINis as follows-

SELECT table1.column1, table2.column2...

FROM table1LEFT JOIN table2

ON table1.common_field table2.common_field!

3.

The Q/ RIGHT JOINreturns all rows from the ri!ht tale) e"en if there are no matches in the

left tale. This means that if the ON clause matches 0 #1ero& records in left tale) the join will

still return a row in the result) ut with NU// in each column from left tale.

7/23/2019 Syntax Join

2/3

This means that a ri!ht join returns all the "alues from the ri!ht tale) plus matched "alues from

the left tale or NU// in case of no matchin! join predicate.

Syntax:

The asic synta, of RIGHT JOINis as follows-

SELECT table1.column1, table2.column2...

FROM table1RI"#T JOIN table2

ON table1.common_field table2.common_field!

4.

The Q/ FULL JOINcomines the results of oth left and ri!ht outer joins.

The joined tale will contain all records from oth tales) and fill in NU//s for missin! matcheson either side.

Syntax:

The asic synta, of FULL JOINis as follows-

SELECT table1.column1, table2.column2...

FROM table1F$LL JOIN table2

ON table1.common_field table2.common_field!

5.

The Q/ SELF JOINis used to join a tale to itself as if the tale were two tales) temporarily

renamin! at least one tale in the Q/ statement.

Syntax:

The asic synta, of SELF JOINis as follows-

SELECT a.column_name, b.column_name...

FROM table1 a, table1 b%#ERE a.common_field b.common_field!

2ere) (2ERE clause could e any !i"en e,pression ased on your requirement.

7/23/2019 Syntax Join

3/3

The CARTESIAN JOINor CROSS JOINreturns the 3artesian product of the sets of records

from the two or more joined tales. Thus) it equates to an inner join where the join'condition

always e"aluates to True or where the join'condition is asent from the statement.

Syntax:

The asic synta, of CARTESIAN JOINor CROSS JOINis as follows-

SELECT table1.column1, table2.column2...FROM table1, table2 &, table' (