Question

tableone

a  |b| c
--------
a1 | |c1
a2 | |c2
a3 | |c3

tabletwo

a | b
-----
a1|b1
a2|b2
a3|b3
a4|b4
a5|b5

merged

a | b | c
a1| b1|c1
a2| b2|c2
a3| b3|c3
a4| b4|
a5| b5|

So I have the two table and I want to merge them. I tried in phpmyadmin these two options:

INSERT IGNORE INTO tableone SELECT * FROM tabletwo;
REPLACE INTO tableone SELECT * FROM tabletwo;

But both do the same (put one table on another), but I want to merge them. So what query must I use? I hope you understand the the question…

Answer 1

Try these queries back-to-back:

INSERT IGNORE INTO tableone (a) SELECT a FROM tabletwo;

UPDATE tableone, tabletwo
SET tableone.b = tabletwo.b
WHERE tableone.a = tabletwo.a;

---

To answer pst, something like this, assuming that tableone does not have a b column:

INSERT INTO tablethree (a, b, c)

SELECT * FROM ((
    SELECT
        tableone.a AS a,
        tabletwo.b AS b,
        tableone.c AS c

    FROM tableone

    LEFT OUTER JOIN tabletwo
    ON tableone.a = tabletwo.a
) UNION (
    SELECT
        tabletwo.a AS a,
        tabletwo.b AS b,
        tableone.c AS c

    FROM tableone

    RIGHT OUTER JOIN tabletwo
    ON tableone.a = tabletwo.a
)) AS x

This is untested, but should work. (“Should”…) The UNION is a workaround for MySQL’s lack of FULL OUTER JOIN.