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Date: Sat, 17 Mar 2007 21:08:33 -0700
From: "Mamta Satoor" <msatoor@gmail.com>
To: "Derby Discussion" <derby-user@db.apache.org>
Subject: Re: Foreign key -- implicit index?
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Yes, that is correct. Copied following from the CREATE INDEX page in Derby's
documentation
Unique, primary key, and foreign key constraints generate indexes that
enforce or "back" the constraint (and are thus sometimes called *backing
indexes*).

Mamta

On 3/17/07, Dan Karp <dkarp@zimbra.com> wrote:
>
> Just to make sure, this foreign key declaration
>
>   CONSTRAINT fk_mail_item_parent_id FOREIGN KEY (mailbox_id, parent_id)
>     REFERENCES ${DATABASE_NAME}.mail_item(mailbox_id, id),
>
> implicitly creates an index on (mailbox_id, parent_id), right?
>

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<div>Yes, that is correct. Copied following from the CREATE INDEX page in Derby&#39;s documentation</div>
<div><span><span>Unique, primary <span style="BACKGROUND: highlight; COLOR: highlighttext">key</span>, and </span><span style="BACKGROUND: highlight; COLOR: highlighttext">foreign</span><span> <span style="BACKGROUND: highlight; COLOR: highlighttext">
key</span> constraints generate indexes that enforce or &quot;back&quot; the constraint (and are thus sometimes called </span></span><em>backing indexes</em><span>).</span></div>
<p><span>Mamta</span><br><br></p>
<div><span class="gmail_quote">On 3/17/07, <b class="gmail_sendername">Dan Karp</b> &lt;<a href="mailto:dkarp@zimbra.com">dkarp@zimbra.com</a>&gt; wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Just to make sure, this foreign key declaration<br><br>&nbsp;&nbsp;CONSTRAINT fk_mail_item_parent_id FOREIGN KEY (mailbox_id, parent_id)
<br>&nbsp;&nbsp;&nbsp;&nbsp;REFERENCES ${DATABASE_NAME}.mail_item(mailbox_id, id),<br><br>implicitly creates an index on (mailbox_id, parent_id), right?<br></blockquote></div><br>

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