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关于mysql学习的 中文教程

</pre>
    <p>This allows some ODBC programs (Delphi, Access) to retrieve the newly inserted row to 
    fetch the <code>AUTO_INCREMENT</code> id. </p>
  </li>
  <li><code>DROP TABLE</code> now waits for all users to free a table before deleting it. </li>
  <li>Fixed small memory leak in the new connect protocol. </li>
  <li>New functions <code>BIN()</code>, <code>OCT()</code>, <code>HEX()</code> and <code>CONV()</code> 
    for converting between different number bases. </li>
  <li>Added function <code>SUBSTRING()</code> with 2 arguments. </li>
  <li>If you created a table with a record length smaller than 5, you couldn't delete rows 
    from the table. </li>
  <li>Added optimization to remove const reference tables from <code>ORDER BY</code> and <code>GROUP 
    BY</code>. </li>
  <li><code>mysqld</code> now automatically disables system locking on Linux and Win32, and 
    for systems that use MIT-pthreads. You can force the use of locking with the <code>--enable-locking</code> 
    option. </li>
  <li>Added <code>--console</code> option to <code>mysqld</code>, to force a console window 
    (for error messages) when using Win32. </li>
  <li>Fixed table locks for Win32. </li>
  <li>Allow <samp>`$'</samp> in identifiers. </li>
  <li>Changed name of user-specific configuration file from <tt>`my.cnf'</tt> to <tt>`.my.cnf'</tt> 
    (Unix only). </li>
  <li>Added <code>DATE_ADD()</code> and <code>DATE_SUB()</code> functions. </li>
</ul>

<h3><a href="manual_toc.html#News-3.22.3" name="News-3.22.3">D.2.26 Changes in release 
3.22.3</a></h3>

<ul>
  <li>Fixed a lock problem (bug in <strong>MySQL</strong> 3.22.1) when closing temporary 
    tables. </li>
  <li>Added missing <code>mysql_ping()</code> to the client library. </li>
  <li>Added <code>--compress</code> option to all <strong>MySQL</strong> clients. </li>
  <li>Changed <code>byte</code> to <code>char</code> in <tt>`mysql.h'</tt> and <tt>`mysql_com.h'</tt>. 
  </li>
</ul>

<h3><a href="manual_toc.html#News-3.22.2" name="News-3.22.2">D.2.27 Changes in release 
3.22.2</a></h3>

<ul>
  <li>Searching on multiple constant keys that matched more than 30% of the rows didn't always 
    use the best possible key. </li>
  <li>New functions <code>&lt;&lt;</code>, <code>&gt;&gt;</code>, <code>RPAD()</code> and <code>LPAD()</code>. 
  </li>
  <li>You can now save default options (like passwords) in a configuration file (<tt>`my.cnf'</tt>). 
  </li>
  <li>Lots of small changes to get <code>ORDER BY</code> to work when no records are found 
    when using fields that are not in <code>GROUP BY</code> (<strong>MySQL</strong> 
    extension). </li>
  <li>Added <code>--chroot</code> option to <code>mysqld</code>, to start <code>mysqld</code> 
    in a chroot environment (by Nikki Chumakov <a href="mailto:[e-mail]">[e-mail]</a>). 
  </li>
  <li>Trailing spaces are now ignored when comparing case-sensitive strings; this should fix 
    some problems with ODBC and flag 512! </li>
  <li>Fixed a core-dump bug in the range optimizer. </li>
  <li>Added <code>--one-thread</code> option to <code>mysqld</code>, for debugging with 
    LinuxThreads (or <code>glibc</code>). (This replaces the <code>-T32</code> flag) </li>
  <li>Added <code>DROP TABLE IF EXISTS</code> to prevent an error from occurring if the table 
    doesn't exist. </li>
  <li><code>IF</code> and <code>EXISTS</code> are now reserved words (they would have to be 
    sooner or later). </li>
  <li>Added lots of new options to <code>mysqldump</code>. </li>
  <li>Server error messages are now in <tt>`mysqld_error.h'</tt>. </li>
  <li>The server/client protocol now supports compression. </li>
  <li>All bug fixes from <strong>MySQL</strong> 3.21.32. </li>
</ul>

<h3><a href="manual_toc.html#News-3.22.1" name="News-3.22.1">D.2.28 Changes in release 
3.22.1</a></h3>

<ul>
  <li>Added new C API function <code>mysql_ping()</code>. </li>
  <li>Added new API functions <code>mysql_init()</code> and <code>mysql_options()</code>. You 
    now MUST call <code>mysql_init()</code> before you call <code>mysql_real_connect()</code>. 
    You don't have to call <code>mysql_init()</code> if you only use <code>mysql_connect()</code>. 
  </li>
  <li>Added <code>mysql_options(...,MYSQL_OPT_CONNECT_TIMEOUT,...)</code> so you can set a 
    timeout for connecting to a server. </li>
  <li>Added <code>--timeout</code> option to <code>mysqladmin</code>, as a test of <code>mysql_options()</code>. 
  </li>
  <li>Added <code>AFTER column</code> and <code>FIRST</code> options to <code>ALTER TABLE ... 
    ADD columns</code>. This makes it possible to add a new column at some specific location 
    within a row in an existing table. </li>
  <li><code>WEEK()</code> now takes an optional argument to allow handling of weeks when the 
    week starts on Monday (some European countries). By default, <code>WEEK()</code> assumes 
    the week starts on Sunday. </li>
  <li><code>TIME</code> columns weren't stored properly (bug in <strong>MySQL</strong> 
    3.22.0). </li>
  <li><code>UPDATE</code> now returns information about how many rows were matched and 
    updated, and how many ``warnings'' occurred when doing the update. </li>
  <li>Fixed incorrect result from <code>FORMAT(-100,2)</code>. </li>
  <li><code>ENUM</code> and <code>SET</code> columns were compared in binary (case-sensitive) 
    fashion; changed to be case insensitive. </li>
</ul>

<h3><a href="manual_toc.html#News-3.22.0" name="News-3.22.0">D.2.29 Changes in release 
3.22.0</a></h3>

<ul>
  <li>New (backward compatible) connect protocol that allows you to specify the database to 
    use when connecting, to get much faster connections to a specific database. The <code>mysql_real_connect()</code> 
    call is changed to: <pre>mysql_real_connect(MYSQL *mysql, const char *host, const char *user,
                   const char *passwd, const char *db, uint port,
                   const char *unix_socket, uint client_flag)
</pre>
  </li>
  <li>Each connection is handled by its own thread, rather than by the master <code>accept()</code> 
    thread. This fixes permanently the telnet bug that was a topic on the mail list some time 
    ago. </li>
  <li>All TCP/IP connections are now checked with backward resolution of the hostname to get 
    better security. <code>mysqld</code> now has a local hostname resolver cache so 
    connections should actually be faster than before, even with this feature. </li>
  <li>A site automatically will be blocked from future connections if someone repeatedly 
    connects with an ``improper header'' (like when one uses telnet). </li>
  <li>You can now refer to tables in different databases with references of the form <code>tbl_name@db_name</code> 
    or <code>db_name.tbl_name</code>. This makes it possible to give a user read access to 
    some tables and write access to others simply by keeping them in different databases! </li>
  <li>Added <code>--user</code> option to <code>mysqld</code>, to allow it to run as another 
    Unix user (if it is started as the Unix <code>root</code> user). </li>
  <li>Added caching of users and access rights (for faster access rights checking) </li>
  <li>Normal users (not anonymous ones) can change their password with <code>mysqladmin 
    password 'new_password'</code>. This uses encrypted passwords that are not logged in the 
    normal <strong>MySQL</strong> log! </li>
  <li>All important string functions are now coded in assembler for x86 Linux machines. This 
    gives a speedup of 10% in many cases. </li>
  <li>For tables that have many columns, the column names are now hashed for much faster 
    column name lookup (this will speed up some benchmark tests a lot!) </li>
  <li>Some benchmarks are changed to get better individual timing. (Some loops were so short 
    that a specific test took &lt; 2 seconds. The loops have been changed to take about 20 
    seconds to make it easier to compare different databases. A test that took 1-2 seconds 
    before now takes 11-24 seconds, which is much better) </li>
  <li>Re-arranged <code>SELECT</code> code to handle some very specific queries involving 
    group functions (like <code>COUNT(*)</code>) without a <code>GROUP BY</code> but with <code>HAVING</code>. 
    The following now works: <pre>mysql&gt; SELECT count(*) as C FROM table HAVING C &gt; 1;
</pre>
  </li>
  <li>Changed the protocol for field functions to be faster and avoid some calls to <code>malloc()</code>. 
  </li>
  <li>Added <code>-T32</code> option to <code>mysqld</code>, for running all queries under the 
    main thread. This makes it possible to debug <code>mysqld</code> under Linux with <code>gdb</code>! 
  </li>
  <li>Added optimization of <code>not_null_column IS NULL</code> (needed for some Access 
    queries). </li>
  <li>Allow <code>STRAIGHT_JOIN</code> to be used between two tables to force the optimizer to 
    join them in a specific order. </li>
  <li>String functions now return <code>VARCHAR</code> rather than <code>CHAR</code> and the 
    column type is now <code>VARCHAR</code> for fields saved as <code>VARCHAR</code>. This 
    should make the <strong>MyODBC</strong> driver better, but may break some old <strong>MySQL</strong> 
    clients that don't handle <code>FIELD_TYPE_VARCHAR</code> the same way as <code>FIELD_TYPE_CHAR</code>. 
  </li>
  <li><code>CREATE INDEX</code> and <code>DROP INDEX</code> are now implemented through <code>ALTER 
    TABLE</code>. <code>CREATE TABLE</code> is still the recommended (fast) way to create 
    indexes. </li>
  <li>Added <code>--set-variable</code> option <code>wait_timeout</code> to <code>mysqld</code>. 
  </li>
  <li>Added time column to <code>mysqladmin processlist</code> to show how long a query has 
    taken or how long a thread has slept. </li>
  <li>Added lots of new variables to <code>show variables</code> and some new to <code>show 
    status</code>. </li>
  <li>Added new type <code>YEAR</code>. <code>YEAR</code> is stored in 1 byte with allowable 
    values of 0, and 1901 to 2155. </li>
  <li>Added new <code>DATE</code> type that is stored in 3 bytes rather than 4 bytes. All new 
    tables are created with the new date type if you don't use the <code>--old-protocol</code> 
    option to <code>mysqld</code>. </li>
  <li>Fixed bug in record caches; for some queries, you could get <code>Error from table 
    handler: #</code> on some operating systems. </li>
  <li>Added <code>--enable-assembler</code> option to <code>configure</code>, for x86 machines 
    (tested on Linux + <code>gcc</code>). This will enable assembler functions for the most 
    important string functions for more speed! </li>
</ul>

<h2><a href="manual_toc.html#News-3.21.x" name="News-3.21.x">D.3 Changes in release 3.21.x</a></h2>

<h3><a href="manual_toc.html#News-3.21.33" name="News-3.21.33">D.3.1 Changes in release 
3.21.33</a></h3>

<ul>
  <li>Fixed problem when sending <code>SIGHUP</code> to <code>mysqld</code>; <code>mysqld</code> 
    core dumped when starting from boot on some systems. </li>
  <li>Fixed problem with losing a little memory for some connections. </li>
  <li><code>DELETE FROM tbl_name</code> without a <code>WHERE</code> condition is now done the 
    long way when you use <code>LOCK TABLES</code> or if the table is in use, to avoid race 
    conditions. </li>
  <li><code>INSERT INTO TABLE (timestamp_column) VALUES (NULL);</code> didn't set timestamp. </li>
</ul>

<h3><a href="manual_toc.html#News-3.21.32" name="News-3.21.32">D.3.2 Changes in release 
3.21.32</a></h3>

<ul>
  <li>Fixed some possible race conditions when doing many reopen/close on the same tables 
    under heavy load! This can happen if you execute <code>mysqladmin refresh</code> often. 
    This could in some very rare cases corrupt the header of the index file and cause error 
    126 or 138. </li>
  <li>Fixed fatal bug in <code>refresh()</code> when running with the <code>--skip-locking</code> 
    option. There was a ``very small'' time gap after a <code>mysqladmin refresh</code> when a 
    table could be corrupted if one thread updated a table while another thread did <code>mysqladmin 
    refresh</code> and another thread started a new update ont the same table before the first 
    thread had finished. A refresh (or <code>--flush-tables</code>) will now not return until 
    all used tables are closed! </li>
  <li><code>SELECT DISTINCT</code> with a <code>WHERE</code> clause that didn't match any rows 
    returned a row in some contexts (bug only in 3.21.31). </li>
  <li><code>GROUP BY</code> + <code>ORDER BY</code> returned one empty row when no rows where 
    found. </li>
  <li>Fixed a bug in the range optimizer that wrote <code>Use_count: Wrong count for ...</code> 
    in the error log file. </li>
</ul>

<h3><a href="manual_toc.html#News-3.21.31" name="News-3.21.31">D.3.3 Changes in release 
3.21.31</a></h3>

<ul>
  <li>Fixed a sign extension problem for the <code>TINYINT</code> type on Irix. </li>
  <li>Fixed problem with <code>LEFT(&quot;constant_string&quot;,function)</code>. </li>
  <li>Fixed prob