The document explains different types of SQL joins, including inner, left, right, full, left excluding, right excluding, and outer excluding joins. For each type of join, it provides a visual representation of the tables being joined, an example SQL query, and a description of the results returned.

1. VISUALIZING
SQL JOIN
V I N C E N T C H A N - D E C 2 0 1 6

2. INNER JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
INNER JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
1 JANE EXECUTIVE
2 MARY MANAGER
3 JOHN SUPERVISOR
Returns all rows when there is at least one
match in BOTH tables

3. LEFT JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
LEFT JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
1 JANE EXECUTIVE
2 MARY MANAGER
3 JOHN SUPERVISOR
4 EMMA NULL
Return all rows from the left table, and the
matched rows from the right table

4. RIGHT JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
RIGHT JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
7 NULL CLERK
2 MARY MANAGER
3 JOHN SUPERVISOR
5 NULL EXECUTIVE
1 JANE EXECUTIVE
Return all rows from the right table, and
the matched rows from the left table

5. FULL OUTER JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
FULL OUTER JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
1 JANE EXECUTIVE
2 MARY MANAGER
3 JOHN SUPERVISOR
4 EMMA NULL
7 NULL CLERK
5 NULL EXECUTIVE
Return all of the records from both tables

6. LEFT EXCLUDING JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
LEFT JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
WHERE POSITION.POSITION IS NULL
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
1 JANE EXECUTIVE
4 EMMA NULL
Return all of the records in the left table
that do not match any records in the right
table

7. RIGHT EXCLUDING JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
RIGHT JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
WHERE STAFF.NAME IS NULL
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
7 NULL CLERK
5 NULL EXECUTIVE
Return all of the records in the right table
that do not match any records in the left
table

8. OUTER EXCLUDING JOIN
TA B L E A TA B L E B
STAFF_ID NAME
1 JANE
2 MARY
3 JOHN
4 EMMA
s t a f f
STAFF_ID POSITION
7 CLERK
2 MANAGER
3 SUPERVISOR
5 EXECUTIVE
1 EXECUTIVE
P O S I T I O N
SELECT STAFF.STAFF_ID, STAFF.NAME, POSITION.POSITION
FROM STAFF
FULL OUTER JOIN POSITION
ON STAFF.STAFF_ID = POSITION.STAFF_ID
R E S U L T
S Q L C O M M A N D
STAFF_ID NAME POSITION
7 NULL CLERK
5 NULL EXECUTIVE
Return all of the records in the left table
and all of the records in the right table that
do not match

9. ALTERNATIVELY
A
INNER
JOIN
=
B 1 B 1
C 2 C 2
3
A
RIGHT
JOIN
=
B 1 B 1
C 2 C 2
3 3
A
LEFT
JOIN
=
A
B 1 B 1
C 2 C 2
3
A
FULL
JOIN
=
A
B 1 B 1
C 2 C 2
3 3