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MySql – copy column between tables

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Oct 28.2005

What would be the MYSQL command to copy contents of one column from one table into a column of another table if a certain condition is true?

For example..

Table t1
Column a
column b

Table t2
column c
column d

I’d like to copy a into c if b=d.

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PHP

2 Comments(s) ↴

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@AneweraOct 31.2005 — //Web 101 - The would be an the INSERT SELECT.


$query = "INSERT INTO table2 (colA,col? SELECT colC,ColD FROM table1 WHERE colC = '$var'";
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@chazzyOct 31.2005 — hi.

anewera's response is wrong, it depends on some external variable and copies both a and b. you only want to copy a into c if b=d.

first build your query to compare:

select b.colC from table a, table b where a.colB = b.colD

this gives you all of the b's that match up.

now we want to UPDATE, since the records already exist.

UPDATE tablea set colA = (select colC from tableb b where b.colD = tablea.col?

that should work.

it depends on B,D being defined as unique keys though.
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