尝试在 MySql 中完全连接两个表

Question

I was trying to full join to tables as the code below,

SELECT C.cust_name,O.ord_num
FROM customers C
  FULL JOIN orders O
  ON C.cust_code = O.cust_code;

but this code is not working.Is anyone can solve this?

Answer 1

You can use:

SELECT C.cust_name, O.ord_num
FROM customers C
LEFT JOIN orders O
  ON C.cust_code = O.cust_code
UNION ALL
SELECT null, O.ord_num
FROM orders O
LEFT JOIN customers C
  ON C.cust_code = O.cust_code
WHERE C.cust_code IS NULL;

Answer 2

FULL OUTER JOIN result without FULL OUTER JOIN support:

SELECT C.cust_name,O.ord_num
FROM customers C
  LEFT JOIN orders O
  ON C.cust_code = O.cust_code
UNION ALL
SELECT NULL, O.ord_num
FROM orders O
WHERE NOT EXISTS (select 1 from customers C where C.cust_code = O.cust_code)

Answer 3

UNION ALL & LEFT JOIN will be equivalent :

SELECT C.cust_name, O.ord_num
FROM customers C LEFT JOIN
     orders O
     ON C.cust_code = O.cust_code
UNION ALL -- Use UNION if you don't want duplicate
SELECT C.cust_name, O.ord_num
FROM orders O LEFT JOIN
     customers C
     ON C.cust_code = O.cust_code;

Answer 4

You are using Full Join in your Query, Correct Query will be:

    SELECT C.cust_name,O.ord_num
    FROM customers C
    FULL OUTER JOIN orders O
    ON C.cust_code = O.cust_code;

There is no such Join FULL JOIN , Correct is FULL OUTER JOIN