MYSQL QUERY LEFT JOIN SHOW ALL DATA FROM ONE TABLE

问题

SELECT 
A.CODE,
B.NOTE,
C.NUMBER

FROM (A
LEFT JOIN B
ON A.CODE = B.CODE
LEFT JOIN C
ON A.CODE = C.NUMBER
)

WHERE C.ID = B.ID 

Need to show some results combined from 3 tables, but my results show all data from table B reported also if the data isn't real from table C.

Table A.code
1
2
3

Table B.code
1
2
3

Table B.note
pippo 
paperino
pluto

Table C.number
1

Ideally there should be one result showing

1  1    pippo

but in results it is shown:

1  1    pippo
1  1    paperino
1  1    pluto

How can I get the real data?

回答1:

SELECT 
A.CODE,
B.NOTE,
C.NUMBER

FROM A
INNER JOIN B ON A.CODE = B.CODE
INNER JOIN C ON A.CODE = C.NUMBER

no need for WHERE cluse

回答2:

You need INNER JOIN

SELECT 
A.CODE,
B.NOTE,
C.NUMBER

FROM C
INNER JOIN B on C.Number=B.Code
INNER JOIN A on B.Code=A.Code

回答3:

LEFT JOIN will take all results from the table mentioned on the left side. Try JOIN instead which is an INNER JOIN afaik

来源：https://stackoverflow.com/questions/17787084/mysql-query-left-join-show-all-data-from-one-table