Comments on: Add Foreign Key in phpMyAdmin http://ivan-grace.com/techblog/2009/01/add-foreign-key-in-phpmyadmin/ Mon, 22 Jun 2009 17:13:48 -0500 http://wordpress.org/?v=2.8 hourly 1 By: Ivan Guan http://ivan-grace.com/techblog/2009/01/add-foreign-key-in-phpmyadmin/comment-page-1/#comment-66 Ivan Guan Sat, 09 May 2009 17:21:01 +0000 http://ivan-grace.com/techblog/2009/01/add-foreign-key-in-phpmyadmin/#comment-66 If you already have the tables somewhere (perhaps in a temporary, non-relational setup), you can use a left join to find "orphaned" rows. This will find records in $t1 that refer to non-existant rows in $t2. Just fill in the variables. SELECT t1.$key FROM $t1 AS t1 LEFT JOIN $t2 AS t2 ON t1.$foreign_key = t2.$key WHERE t2.$key IS NULL If you already have the tables somewhere (perhaps in a temporary, non-relational setup), you can use a left join to find “orphaned” rows. This will find records in $t1 that refer to non-existant rows in $t2. Just fill in the variables.

SELECT t1.$key
FROM $t1 AS t1
LEFT JOIN $t2 AS t2
ON t1.$foreign_key = t2.$key
WHERE t2.$key IS NULL

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