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gnosygnu
2017-04-27 21:02:09 -04:00
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@@ -62,7 +62,7 @@
</ul>
</div>
<h3>
<span class="mw-headline" id="Avoid_LIKE">Avoid LIKE</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Avoid_LIKE" title="Edit section: Avoid_LIKE" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Avoid_LIKE">Avoid LIKE</span>
</h3>
<ul>
<li>
@@ -94,7 +94,7 @@ WHERE name LIKE 'a%';
The clause <code>name LIKE 'a%'</code> does not use the index <code>tbl1__name</code>.
</p>
<h3>
<span class="mw-headline" id="Alternative:_Use_comparison">= Alternative: Use comparison</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Alternative:_Use_comparison" title="Edit section: Alternative:_Use_comparison" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Alternative:_Use_comparison">= Alternative: Use comparison</span>
</h3>
<p>
If the like has a wildcard at the end, and the data is standardized to one case (all lowercase or all uppercase), use an equality instead:
@@ -108,7 +108,7 @@ WHERE name &gt;= 'a' AND name &lt; 'b';
This uses the index <code>tbl1__name</code> and returns the same data.
</p>
<h3>
<span class="mw-headline" id="Avoid_ORDER_BY">Avoid ORDER BY</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Avoid_ORDER_BY" title="Edit section: Avoid_ORDER_BY" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Avoid_ORDER_BY">Avoid ORDER BY</span>
</h3>
<p>
ORDER BY will do an expensive sort operation which may not use an index. This will come into play with multiple-table joins
@@ -124,13 +124,13 @@ ORDER BY t2.age
In most cases, SQLite will only apply one index. In this example, it will be the index for the JOIN. No index gets applied for the score column, even if one is available In some cases, SQLite will actually sort the result-set by the ORDER BY first, before it applies the WHERE.
</p>
<h4>
<span class="mw-headline" id="Alternative:_denormalize_the_table">Alternative: denormalize the table</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Alternative:_denormalize_the_table" title="Edit section: Alternative:_denormalize_the_table" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Alternative:_denormalize_the_table">Alternative: denormalize the table</span>
</h4>
<p>
Putting all the columns in one table and building an index across them.
</p>
<h4>
<span class="mw-headline" id="Alternative:_multiple_where_clauses">Alternative: multiple where clauses</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Alternative:_multiple_where_clauses" title="Edit section: Alternative:_multiple_where_clauses" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Alternative:_multiple_where_clauses">Alternative: multiple where clauses</span>
</h4>
<pre>
SELECT t1.id
@@ -145,7 +145,7 @@ WHERE t2.age &gt; 70 AND t2.age &lt;= 100
;
</pre>
<h3>
<span class="mw-headline" id="Beware_bulk_INSERTs_into_a_table_with_a_PRIMARY_KEY">Beware bulk INSERTs into a table with a PRIMARY KEY</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Beware_bulk_INSERTs_into_a_table_with_a_PRIMARY_KEY" title="Edit section: Beware_bulk_INSERTs_into_a_table_with_a_PRIMARY_KEY" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Beware_bulk_INSERTs_into_a_table_with_a_PRIMARY_KEY">Beware bulk INSERTs into a table with a PRIMARY KEY</span>
</h3>
<pre>
INSERT INTO
@@ -161,7 +161,7 @@ WHERE t2.age &gt; 100 AND t2.age &lt;= 130
Instead, insert into the table with an ORDER BY
</p>
<h3>
<span class="mw-headline" id="ATTACH">ATTACH</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=ATTACH" title="Edit section: ATTACH" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="ATTACH">ATTACH</span>
</h3>
<p>
ATTACH database does not affect performance. There is no difference between the following
@@ -180,19 +180,19 @@ FROM tbl1 t1
;
</pre>
<h2>
<span class="mw-headline" id="Get_a_Solid_State_Drive">Get a Solid State Drive</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Get_a_Solid_State_Drive" title="Edit section: Get_a_Solid_State_Drive" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Get_a_Solid_State_Drive">Get a Solid State Drive</span>
</h2>
<p>
SQLite does a lot of disk reading and writing
</p>
<h2>
<span class="mw-headline" id="Use_an_INDEX_for_your_SELECTs.2C_especially_JOINs">Use an INDEX for your SELECTs, especially JOINs</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Use_an_INDEX_for_your_SELECTs.2C_especially_JOINs" title="Edit section: Use_an_INDEX_for_your_SELECTs.2C_especially_JOINs" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Use_an_INDEX_for_your_SELECTs.2C_especially_JOINs">Use an INDEX for your SELECTs, especially JOINs</span>
</h2>
<h2>
<span class="mw-headline" id="Use_TRANSACTIONs_for_multiple_INSERT_.2F_UPDATE_.2F_DELETE">Use TRANSACTIONs for multiple INSERT / UPDATE / DELETE</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Use_TRANSACTIONs_for_multiple_INSERT_.2F_UPDATE_.2F_DELETE" title="Edit section: Use_TRANSACTIONs_for_multiple_INSERT_.2F_UPDATE_.2F_DELETE" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Use_TRANSACTIONs_for_multiple_INSERT_.2F_UPDATE_.2F_DELETE">Use TRANSACTIONs for multiple INSERT / UPDATE / DELETE</span>
</h2>
<h2>
<span class="mw-headline" id="Use_PRAGMA_page_size_4096">Use PRAGMA page_size 4096</span> <span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/wiki/Dev/Sqlite/Tips?action=edit&amp;section_key=Use_PRAGMA_page_size_4096" title="Edit section: Use_PRAGMA_page_size_4096" class="xowa-hover-off">edit</a><span class="mw-editsection-bracket">]</span></span>
<span class="mw-headline" id="Use_PRAGMA_page_size_4096">Use PRAGMA page_size 4096</span>
</h2>
</div>