Adding a unique key to Drupal column

Question

I'm just doing a one-off script, but I'm wondering if there's a correct "Drupal way" to alter a table and a unique key.

For example, this is essentially the query I want to do:

ALTER IGNORE TABLE `node_revision` ADD UNIQUE(`hash`);

And then if I later wanted to remove the unique index on hash, how would I also do that?

Does it have something to do with updating the database schema? or possibly db_change_field()?

Jesse Pinho · Accepted Answer · 2014-02-26 17:53:25Z

2

db_add_unique_key() is the function you're looking for.

answered Feb 26, 2014 at 17:39

Jesse Pinho

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Community · Accepted Answer · 2017-04-13 12:46:58Z

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You can use hook_schema_alter and db_add_field in the hook_install of your module to modify exists tables.

This question is on on that exact subject.

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answered Feb 26, 2014 at 16:21

Felix Eve

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I don't actually want to add the field, though, the field will already be added. I just want to add the fact that the column is unique.
– Jack Ryan
Commented Feb 26, 2014 at 16:29
Oh, sorry. My bad. You were already on the right track with db_change_field.
– Felix Eve
Commented Feb 26, 2014 at 16:33
I'm not quite seeing how I would add the unique modifier though. How would I do that with db_change_field()?
– Jack Ryan
Commented Feb 26, 2014 at 16:47
Would it just be something like db_change_field('node_revision', 'hash', 'hash', array(), array('Unique' => array('hash')))
– Jack Ryan
Commented Feb 26, 2014 at 16:49
See this page. "unique keys" is the array key you want to use. Also you need to pass in an associative array here.
– Felix Eve
Commented Feb 26, 2014 at 16:54

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