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+<title>Rowid Tables</title>
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+
+
+<h1 align="center">Rowid Tables</h1>
+
+<h2>1.0 Definition</h2>
+
+<p>A "rowid table" is any table in an SQLite schema that
+<ul>
+<li>is <em>not</em> a <a href="vtab.html">virtual table</a>, and
+<li>is <em>not</em> a <a href="withoutrowid.html">WITHOUT ROWID</a> table.
+</ul>
+Most tables in a typical SQLite database schema are rowid tables.
+
+<p>Rowid tables are distinguished by the fact that they all have
+a unique, non-NULL, signed 64-bit integer <a href="lang_createtable.html#rowid">rowid</a> that is used as
+the access key for the data in the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine.
+
+<h2>2.0 Quirks</h2>
+
+<ul>
+<li><p>
+The <a href="lang_createtable.html#primkeyconst">PRIMARY KEY</a> of a rowid table (if there is one) is usually not the
+true primary key for the table, in the sense that it is not the unique
+key used by the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine.  The exception to
+this rule is when the rowid table declares an <a href="lang_createtable.html#rowid">INTEGER PRIMARY KEY</a>.
+In the exception, the INTEGER PRIMARY KEY becomes an alias for the 
+<a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+The true primary key for a rowid table (the value that is used as the
+key to look up rows in the underlying <a href="fileformat2.html#btree">B-tree</a> storage engine)
+is the <a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+The PRIMARY KEY constraint for a rowid table (as long as it is not
+the true primary key or INTEGER PRIMARY KEY) is really the same thing
+as a <a href="lang_createtable.html#uniqueconst">UNIQUE constraint</a>.  Because it is not a true primary key,
+columns of the PRIMARY KEY are allowed to be NULL, in violation of
+all SQL standards.
+
+<li><p>
+The <a href="lang_createtable.html#rowid">rowid</a> of a rowid table can be accessed (or changed) by reading or
+writing to any of the "rowid" or "oid" or "_rowid_" columns.  Except,
+if there is a declared columns in the table that use those
+special names, then those names refer to the declared columns, not to
+the underlying <a href="lang_createtable.html#rowid">rowid</a>.
+
+<li><p>
+Access to records via <a href="lang_createtable.html#rowid">rowid</a> is highly optimized and very fast.
+
+<li><p>
+If the <a href="lang_createtable.html#rowid">rowid</a> is not aliased by <a href="lang_createtable.html#rowid">INTEGER PRIMARY KEY</a> then it is not
+persistent and might change.  In particular the <a href="lang_vacuum.html">VACUUM</a> command will
+change rowids for tables that do not declare an INTEGER PRIMARY KEY.
+Therefore, applications should not normally access the rowid directly,
+but instead use an INTEGER PRIMARY KEY.
+
+<li><p>
+In the underlying <a href="fileformat2.html">file format</a>, each rowid is stored as a
+<a href="fileformat2.html#varint">variable-length integer</a>.  That means that small non-negative
+rowid values take up less disk space than large or negative
+rowid values.
+
+<li><p>
+All of the complications above (and others not mentioned here)
+arise from the need to preserve backwards
+compatibility for the hundreds of billions of SQLite database files in
+circulation.  In a perfect world, there would be no such thing as a "rowid"
+and all tables would following the standard semantics implemented as
+<a href="withoutrowid.html">WITHOUT ROWID</a> tables, only without the extra "WITHOUT ROWID" keywords.
+Unfortunately, life is messy.  The designer of SQLite offers his
+sincere apology for the current mess.
+</ul>
+<p align="center"><small><i>This page last modified on  <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink"  data-href="https://sqlite.org/docsrc/finfo/pages/rowidtable.in?m=d768bc62ed">2022-01-08 05:02:57</a> UTC </small></i></p>
+