Connor at 09:33, 8 August 2012

2012-08-08T09:33:53Z

Connor: Created page with "
Here you are shown how to combine multiple queries.

Both related and unrelated queries can be merged,

if the queries are often used together then combining th..."

2012-08-08T09:32:50Z

Created page with "<p>Here you are shown how to combine multiple queries.</p> <p>Both related and unrelated queries can be merged,</p> <p>if the queries are often used together then combining th..."

New page

<p>Here you are shown how to combine multiple queries.</p>
<p>Both related and unrelated queries can be merged,</p>
<p>if the queries are often used together then combining them together can greatly improve performence.</p>
<p>Table 1 and 2 show the two separate tables and Table 3 shows the result you would obtain from combining queries.</p>
<div class="ref_section">
<table class= "db_ref">
<caption>Table 1</caption>
<tr><th>'''content'''</th><th>'''Page name'''</th></tr>
<tr><td>hello</td><td>index.html</td></tr>
<tr><td>Hia</td><td>index.html</td></tr>
<tr><td>page2</td><td>p2.html</td></tr>
<tr><td>Index</td><td>contents.html</td></tr>
</table>
<table class= "db_ref">
<caption>Table 2</caption>
<tr><th>'''Message'''</th></tr>
<tr><td>The site will be down on Tuesday</td></tr>
</table>
<table class= "db_ref">
<caption>Table 3</caption>
<tr><th>'''pagename'''</th><th>'''content'''</th><th>'''NULL'''</th><th>'''page'''</th></tr>
<tr><td>index.html</td><td>hello</td><td></td><td>page</td></tr>
<tr><td>index.html</td><td>Hia</td><td></td><td>page</td></tr>
<tr><td></td><td></td><td>The site will be down on Tuesday</td><td>motd</td></tr>
</table>
</div>
<div class='ht'>
<div class=params>schema:scott</div>
<source lang=sql class='tidy'>DROP TABLE page;
DROP TABLE motd;</source>
<source lang=sql class='setup'> CREATE TABLE page (
content TEXT,
pagename TEXT );
INSERT INTO page VALUES ('hello','index.html');
INSERT INTO page VALUES ('Hia','index.html');
INSERT INTO page VALUES ('page2','p2.html');
INSERT INTO page VALUES ('Index','contents.html');
CREATE TABLE motd (
message VARCHAR(100));
INSERT INTO motd VALUES ('The site will be down on Tuesday');
</source>
<div>
In this example a typical approach to these tables could be:
SELECT pagename, content
FROM page
WHERE pagename = 'index.html'
or:
SELECT message FROM motd
These two queries can be combined using <code>UNION</code> and <code>NULLs</code> where necessary
and therefore a single query can be run allowing a quicker response from the database.
</div>
<source lang='sql' class='def'>
SELECT pagename, content, NULL, 'page'
FROM page
WHERE pagename = 'index.html'
UNION
SELECT NULL, NULL, message, 'motd'
FROM motd</source>
<div class="ecomm e-oracle" style="display: none"></div>
</div>

{{Hacks Ref}}

@@ Line 1: / Line 1: @@
 <p>Here you are shown how to combine multiple queries.</p>
 <p>Both related and unrelated queries can be merged,</p>
-<p>if the queries are often used together then combining them together can greatly improve performence.</p>
+<p>if the queries are often used together then combining them together can greatly improve performance.</p>
 <p>Table 1 and 2 show the two separate tables and Table 3 shows the result you would obtain from combining queries.</p>
 <div class="ref_section">

Combine queries - Revision history

Connor at 09:33, 8 August 2012

Connor: Created page with "Here you are shown how to combine multiple queries. Both related and unrelated queries can be merged, if the queries are often used together then combining th..."

Connor: Created page with "
Here you are shown how to combine multiple queries.

Both related and unrelated queries can be merged,

if the queries are often used together then combining th..."