I'm, generating a SQL query like this in PHP:
$sql = sprintf("UPDATE %s SET %s = %s WHERE %s = %s", ...);
Since almost every part of this query is dynamic I need a way to determine the table's primary key dynamically, so that I'd have a query like this:
$sql = sprintf("UPDATE %s SET %s=%s WHERE PRIMARY_KEY = %s", ...);
Is there a MySQL keyword for a table's primary key, or a way to get it?
I've used the information_schema DB before to find information like this, but it'd be nice if I didn't have to resort to that.
A foreign key, simply stated, is another table's primary key.
SHOW INDEX FROM <tablename>
You want the row where Key_name = PRIMARY
http://dev.mysql.com/doc/refman/5.0/en/show-index.html
You'll probably want to cache the results -- it takes a while to run SHOW statements on all the tables you might need to work with.
It might be not advised but works just fine:
SHOW INDEX FROM <table_name> WHERE Key_name = 'PRIMARY';
The solid way is to use information_schema:
SELECT k.COLUMN_NAME
FROM information_schema.table_constraints t
LEFT JOIN information_schema.key_column_usage k
USING(constraint_name,table_schema,table_name)
WHERE t.constraint_type='PRIMARY KEY'
AND t.table_schema=DATABASE()
AND t.table_name='owalog';
As presented on the mysql-list. However its a few times slower from the first solution.
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