移动版的今日插件可以显示星期啦，哈哈！不过联通版的不知道一样不，估计应该差不多！
1.首先找到windows目录下的_application.xml，找到<DateDataView hittable="false" x="12" y="30" width="120" height="16" size="12" dataProvider="dateTime" />这一行，在这行下面新加一行<NumberDataView hittable="false" x="106" y="30" width="25" height="16" numberResourceName="DayOfWeek" digiCount="1" dataProvider="dateTime" dataKey="DAYOFWEEK" />
2.将附件中的CCI_Td01.tga复制到windows目录下替换！
ok！重启吧，看看星期出来了吧，呵呵！
就是在日期的后面加了个星期，就不截图了，显示格式为：十二月 16, 2009 （三）
点击下载此文件以下是调用腾讯网站天气预告的代码，引用脚本在下面的附件中！
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>天气</title>
</head>
<body>
<style type="text/css">
#Wealth{line-height:18px;height:66px;padding-bottom:10px; float:left; cursor:pointer;width:207px; background:url(../images/info_18.gif) no-repeat 0px 5px;}
#Wealth *{line-height:18px;}
#Wealth h6{font-size:12px; margin:0 auto; padding-top:10px;}
#Wealth span.img{float:left;display:block;padding-top:8px}
#Wealth p{float:left;margin:0;padding:0; height:0px;}
#Wealth div{font-size:12px;width:100px;}
</style>
<script language="javascript">
function loadPng(o){
if(MiniSite.Browser.ie){
try{
var img = o;
var imgName = o.src.toUpperCase();
if (imgName.substring(imgName.length-3, imgName.length) == "PNG"){
var imgID = (img.id) ? "id='" + img.id + "' " : "";
var imgClass = (img.className) ? "class='" + img.className + "' " : "";
var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' ";
var imgStyle = "display:inline-block;" + img.style.cssText;
if (img.align == "left") imgStyle = "float:left;" + imgStyle;
if (img.align == "right") imgStyle = "float:right;" + imgStyle;
if (img.parentElement.href) imgStyle = "cursor:hand;" + imgStyle ;
var strNewHTML = "<span " + imgID + imgClass + imgTitle + " style=\"" + "width:" + img.width + "px; height:" + img.height + "px;" + imgStyle + ";" + "filter:progid:DXImageTransform.Microsoft.AlphaImageLoader" + "(src=\'" + img.src + "\', sizingMethod='image');\"></span>";
img.outerHTML = strNewHTML;
}
}catch (e){}
}
}
</script>
<script type="text/javascript" src="j.soso.weather_utf8.js"></script>
</head>
<body>
<div id="Wealth"></div>
<script type="text/javascript">
/*<![CDATA[*/
MiniSite.Weather.print("Wealth");
/*]]>*/
</script>
</body>
</html>
然而，尽管大规模程序的开发对 Adobe 可能是好的，可以肯定它未必对任何人都可行，传统程序语言就是一个例子。
对任何 Java 程序开发正规军来说，强类型，包装，以及命名空间尽管对维护大型程序来说可能很容易，但对 Web 程序员来说几乎没有什么用处，Web 程序员仅仅想通过编程对 UI 搞一点花样。
事实上，ECMAScript 委员会想创造一种万能编程语言的初衷非常值得置疑，曾经，有一群非常聪明的人联合起来，想写一个终极语言，这种语言非常安全，有活力，且非常标准化，几乎没有需要解释的地方，这就是 Ada，现在没有人还记得 Ada，因为这种语言非常严格，缺乏灵活，人们宁愿使用 C。
既然没有人能够创造一个终极的，完美的传统编程语言，又怎么能指望我们可以为 Web 创造一个这样的语言？我们越多讨论大规模 Web 程序，越应该知道，单一的编程语言将永远无法适合任何工作。
作者非常喜欢 Model-View-Controller 设计模式，然而这个模式并不适合于任何场合，不过这个模式可以为程序开发提供一套指南，总体上说，Model-View-Controller 的核心是从数据层，业务逻辑层，分离展示层。浏览器可以算作 View （展示层），我们不应强迫它同时成为业务逻辑层。
自从有了 Javascript，我们对它的指望越来越多，企图用它来创建整个程序，事实上，Javascript 不可能适合任何任务。我们不应该将越来越多的业务功能硬塞进浏览器，应该让浏览器专心作展示，而在其它地方展开业务逻辑。
比如，插件。当然，很多 Web 开发者会告诉你插件不是好东西，每次你强迫用户下载安装插件，都相当于在你的代码前面设置了障碍，事实是这样吗？
早期的插件绝大多数用来提供多媒体功能，很快就成为在线营销工具，那时，人们使用拨号上网，但很少有人怀疑人们对插件的耐心。
现在的例子是 Google Gears，一次性安装 Google Gears，任何基于 Google Gears 的程序都获得额外的功能。目前，基于 Google Gears 的站点不仅包含 Goolge Docs 与 Google Reader，也包含 MySpace, Picasa 甚至 Wordpress。
人们倾向于 Google Gears 的离线运行 Web 程序的能力，却忽视了 WorkerPool 模块，WorkerPool 允许 Javascript 在后台执行，独立于网页代码。WorkerPool 是独立的代码执行引擎，只不过刚好象普通浏览器那样运行相同的 Javascript 代码。
为什么要用 JavaScript，而不是 Python, Lisp 或其它。如果有一种应用有足够的说服力，就有足够的动力将它设计成插件，尤其是在现在的宽带世界。这样的例子已经存在，Adobe的 Flash 插件就可以执行 ECMAScript 4 标准的脚本，其它平台还包括 Curl 与 REBOL。
作为 Web 开发者，我们羞于选择其它道路，只是在无休止地对 JavaScript 进行改进和标准化。因为那是 Web 标准，我们告诉自己，JavaScript 是一个纯净的选项。
但如果只拘泥于单一的方式，我们为什么还要费这番力气？我们已经拥有一个功能齐备的客户端做任何事情，从数据库，到 e-mail，它已经安装到成千上万的企业，这就是 LotusNotes。
这就是我们前进的方向？这就是将来的浏览器模型？或者，对 Web 开发界来说，我们是否应该跳出这个圈子思考问题？
]]>以下是修改日志:
======================= Release 2.3.0 2008-01-23 =======================
Changes in runtime behavior
1. LUCENE-994: Defaults for IndexWriter have been changed to maximize
out-of-the-box indexing speed. First, IndexWriter now flushes by
RAM usage (16 MB by default) instead of a fixed doc count (call
IndexWriter.setMaxBufferedDocs to get backwards compatible
behavior). Second, ConcurrentMergeScheduler is used to run merges
using background threads (call IndexWriter.setMergeScheduler(new
SerialMergeScheduler()) to get backwards compatible behavior).
Third, merges are chosen based on size in bytes of each segment
rather than document count of each segment (call
IndexWriter.setMergePolicy(new LogDocMergePolicy()) to get
backwards compatible behavior).
NOTE: users of ParallelReader must change back all of these
defaults in order to ensure the docIDs "align" across all parallel
indices.
(Mike McCandless)
2. LUCENE-1045: SortField.AUTO didn't work with long. When detecting
the field type for sorting automatically, numbers used to be
interpreted as int, then as float, if parsing the number as an int
failed. Now the detection checks for int, then for long,
then for float. (Daniel Naber)
API Changes
1. LUCENE-843: Added IndexWriter.setRAMBufferSizeMB(...) to have
IndexWriter flush whenever the buffered documents are using more
than the specified amount of RAM. Also added new APIs to Token
that allow one to set a char[] plus offset and length to specify a
token (to avoid creating a new String() for each Token). (Mike
McCandless)
2. LUCENE-963: Add setters to Field to allow for re-using a single
Field instance during indexing. This is a sizable performance
gain, especially for small documents. (Mike McCandless)
3. LUCENE-969: Add new APIs to Token, TokenStream and Analyzer to
permit re-using of Token and TokenStream instances during
indexing. Changed Token to use a char[] as the store for the
termText instead of String. This gives faster tokenization
performance (~10-15%). (Mike McCandless)
4. LUCENE-847: Factored MergePolicy, which determines which merges
should take place and when, as well as MergeScheduler, which
determines when the selected merges should actually run, out of
IndexWriter. The default merge policy is now
LogByteSizeMergePolicy (see LUCENE-845) and the default merge
scheduler is now ConcurrentMergeScheduler (see
LUCENE-870). (Steven Parkes via Mike McCandless)
5. LUCENE-1052: Add IndexReader.setTermInfosIndexDivisor(int) method
that allows you to reduce memory usage of the termInfos by further
sub-sampling (over the termIndexInterval that was used during
indexing) which terms are loaded into memory. (Chuck Williams,
Doug Cutting via Mike McCandless)
6. LUCENE-743: Add IndexReader.reopen() method that re-opens an
existing IndexReader (see New features -> 8.) (Michael Busch)
7. LUCENE-1062: Add setData(byte[] data),
setData(byte[] data, int offset, int length), getData(), getOffset()
and clone() methods to o.a.l.index.Payload. Also add the field name
as arg to Similarity.scorePayload(). (Michael Busch)
8. LUCENE-982: Add IndexWriter.optimize(int maxNumSegments) method to
"partially optimize" an index down to maxNumSegments segments.
(Mike McCandless)
9. LUCENE-1080: Changed Token.DEFAULT_TYPE to be public.
10. LUCENE-1064: Changed TopDocs constructor to be public.
(Shai Erera via Michael Busch)
11. LUCENE-1079: DocValues cleanup: constructor now has no params,
and getInnerArray() now throws UnsupportedOperationException (Doron Cohen)
12. LUCENE-1089: Added PriorityQueue.insertWithOverflow, which returns
the Object (if any) that was bumped from the queue to allow
re-use. (Shai Erera via Mike McCandless)
13. LUCENE-1101: Token reuse 'contract' (defined LUCENE-969)
modified so it is token producer's responsibility
to call Token.clear(). (Doron Cohen)
14. LUCENE-1118: Changed StandardAnalyzer to skip too-long (default >
255 characters) tokens. You can increase this limit by calling
StandardAnalyzer.setMaxTokenLength(...). (Michael McCandless)
Bug fixes
1. LUCENE-933: QueryParser fixed to not produce empty sub
BooleanQueries "()" even if the Analyzer produced no
tokens for input. (Doron Cohen)
2. LUCENE-955: Fixed SegmentTermPositions to work correctly with the
first term in the dictionary. (Michael Busch)
3. LUCENE-951: Fixed NullPointerException in MultiLevelSkipListReader
that was thrown after a call of TermPositions.seek().
(Rich Johnson via Michael Busch)
4. LUCENE-938: Fixed cases where an unhandled exception in
IndexWriter's methods could cause deletes to be lost.
(Steven Parkes via Mike McCandless)
5. LUCENE-962: Fixed case where an unhandled exception in
IndexWriter.addDocument or IndexWriter.updateDocument could cause
unreferenced files in the index to not be deleted
(Steven Parkes via Mike McCandless)
6. LUCENE-957: RAMDirectory fixed to properly handle directories
larger than Integer.MAX_VALUE. (Doron Cohen)
7. LUCENE-781: MultiReader fixed to not throw NPE if isCurrent(),
isOptimized() or getVersion() is called. Separated MultiReader
into two classes: MultiSegmentReader extends IndexReader, is
package-protected and is created automatically by IndexReader.open()
in case the index has multiple segments. The public MultiReader
now extends MultiSegmentReader and is intended to be used by users
who want to add their own subreaders. (Daniel Naber, Michael Busch)
8. LUCENE-970: FilterIndexReader now implements isOptimized(). Before
a call of isOptimized() would throw a NPE. (Michael Busch)
9. LUCENE-832: ParallelReader fixed to not throw NPE if isCurrent(),
isOptimized() or getVersion() is called. (Michael Busch)
10. LUCENE-948: Fix FNFE exception caused by stale NFS client
directory listing caches when writers on different machines are
sharing an index over NFS and using a custom deletion policy (Mike
McCandless)
11. LUCENE-978: Ensure TermInfosReader, FieldsReader, and FieldsReader
close any streams they had opened if an exception is hit in the
constructor. (Ning Li via Mike McCandless)
12. LUCENE-985: If an extremely long term is in a doc (> 16383 chars),
we now throw an IllegalArgumentException saying the term is too
long, instead of cryptic ArrayIndexOutOfBoundsException. (Karl
Wettin via Mike McCandless)
13. LUCENE-991: The explain() method of BoostingTermQuery had errors
when no payloads were present on a document. (Peter Keegan via
Grant Ingersoll)
14. LUCENE-992: Fixed IndexWriter.updateDocument to be atomic again
(this was broken by LUCENE-843). (Ning Li via Mike McCandless)
15. LUCENE-1008: Fixed corruption case when document with no term
vector fields is added after documents with term vector fields.
This bug was introduced with LUCENE-843. (Grant Ingersoll via
Mike McCandless)
16. LUCENE-1006: Fixed QueryParser to accept a "" field value (zero
length quoted string.) (yonik)
17. LUCENE-1010: Fixed corruption case when document with no term
vector fields is added after documents with term vector fields.
This case is hit during merge and would cause an EOFException.
This bug was introduced with LUCENE-984. (Andi Vajda via Mike
McCandless)
19. LUCENE-1009: Fix merge slowdown with LogByteSizeMergePolicy when
autoCommit=false and documents are using stored fields and/or term
vectors. (Mark Miller via Mike McCandless)
20. LUCENE-1011: Fixed corruption case when two or more machines,
sharing an index over NFS, can be writers in quick succession.
(Patrick Kimber via Mike McCandless)
21. LUCENE-1028: Fixed Weight serialization for few queries:
DisjunctionMaxQuery, ValueSourceQuery, CustomScoreQuery.
Serialization check added for all queries.
(Kyle Maxwell via Doron Cohen)
22. LUCENE-1048: Fixed incorrect behavior in Lock.obtain(...) when the
timeout argument is very large (eg Long.MAX_VALUE). Also added
Lock.LOCK_OBTAIN_WAIT_FOREVER constant to never timeout. (Nikolay
Diakov via Mike McCandless)
23. LUCENE-1050: Throw LockReleaseFailedException in
Simple/NativeFSLockFactory if we fail to delete the lock file when
releasing the lock. (Nikolay Diakov via Mike McCandless)
24. LUCENE-1071: Fixed SegmentMerger to correctly set payload bit in
the merged segment. (Michael Busch)
25. LUCENE-1042: Remove throwing of IOException in getTermFreqVector(int, String, TermVectorMapper) to be consistent
with other getTermFreqVector calls. Also removed the throwing of the other IOException in that method to be consistent. (Karl Wettin via Grant Ingersoll)
26. LUCENE-1096: Fixed Hits behavior when hits' docs are deleted
along with iterating the hits. Deleting docs already retrieved
now works seamlessly. If docs not yet retrieved are deleted
(e.g. from another thread), and then, relying on the initial
Hits.length(), an application attempts to retrieve more hits
than actually exist , a ConcurrentMidificationException
is thrown. (Doron Cohen)
27. LUCENE-1068: Changed StandardTokenizer to fix an issue with it marking
the type of some tokens incorrectly. This is done by adding a new flag named
replaceInvalidAcronym which defaults to false, the current, incorrect behavior. Setting
this flag to true fixes the problem. This flag is a temporary fix and is already
marked as being deprecated. 3.x will implement the correct approach. (Shai Erera via Grant Ingersoll)
LUCENE-1140: Fixed NPE caused by 1068 (Alexei Dets via Grant Ingersoll)
28. LUCENE-749: ChainedFilter behavior fixed when logic of
first filter is ANDNOT. (Antonio Bruno via Doron Cohen)
29. LUCENE-508: Make sure SegmentTermEnum.prev() is accurate (= last
term) after next() returns false. (Steven Tamm via Mike
McCandless)
New features
1. LUCENE-906: Elision filter for French.
(Mathieu Lecarme via Otis Gospodnetic)
2. LUCENE-960: Added a SpanQueryFilter and related classes to allow for
not only filtering, but knowing where in a Document a Filter matches
(Grant Ingersoll)
3. LUCENE-868: Added new Term Vector access features. New callback
mechanism allows application to define how and where to read Term
Vectors from disk. This implementation contains several extensions
of the new abstract TermVectorMapper class. The new API should be
back-compatible. No changes in the actual storage of Term Vectors
has taken place.
3.1 LUCENE-1038: Added setDocumentNumber() method to TermVectorMapper
to provide information about what document is being accessed.
(Karl Wettin via Grant Ingersoll)
4. LUCENE-975: Added PositionBasedTermVectorMapper that allows for
position based lookup of term vector information.
See item #3 above (LUCENE-868).
5. LUCENE-1011: Added simple tools (all in org.apache.lucene.store)
to verify that locking is working properly. LockVerifyServer runs
a separate server to verify locks. LockStressTest runs a simple
tool that rapidly obtains and releases locks.
VerifyingLockFactory is a LockFactory that wraps any other
LockFactory and consults the LockVerifyServer whenever a lock is
obtained or released, throwing an exception if an illegal lock
obtain occurred. (Patrick Kimber via Mike McCandless)
6. LUCENE-1015: Added FieldCache extension (ExtendedFieldCache) to
support doubles and longs. Added support into SortField for sorting
on doubles and longs as well. (Grant Ingersoll)
7. LUCENE-1020: Created basic index checking & repair tool
(o.a.l.index.CheckIndex). When run without -fix it does a
detailed test of all segments in the index and reports summary
information and any errors it hit. With -fix it will remove
segments that had errors. (Mike McCandless)
8. LUCENE-743: Add IndexReader.reopen() method that re-opens an
existing IndexReader by only loading those portions of an index
that have changed since the reader was (re)opened. reopen() can
be significantly faster than open(), depending on the amount of
index changes. SegmentReader, MultiSegmentReader, MultiReader,
and ParallelReader implement reopen(). (Michael Busch)
9. LUCENE-1040: CharArraySet useful for efficiently checking
set membership of text specified by char[]. (yonik)
10. LUCENE-1073: Created SnapshotDeletionPolicy to facilitate taking a
live backup of an index without pausing indexing. (Mike
McCandless)
11. LUCENE-1019: CustomScoreQuery enhanced to support multiple
ValueSource queries. (Kyle Maxwell via Doron Cohen)
12. LUCENE-1095: Added an option to StopFilter to increase
positionIncrement of the token succeeding a stopped token.
Disabled by default. Similar option added to QueryParser
to consider token positions when creating PhraseQuery
and MultiPhraseQuery. Disabled by default (so by default
the query parser ignores position increments).
(Doron Cohen)
Optimizations
1. LUCENE-937: CachingTokenFilter now uses an iterator to access the
Tokens that are cached in the LinkedList. This increases performance
significantly, especially when the number of Tokens is large.
(Mark Miller via Michael Busch)
2. LUCENE-843: Substantial optimizations to improve how IndexWriter
uses RAM for buffering documents and to speed up indexing (2X-8X
faster). A single shared hash table now records the in-memory
postings per unique term and is directly flushed into a single
segment. (Mike McCandless)
3. LUCENE-892: Fixed extra "buffer to buffer copy" that sometimes
takes place when using compound files. (Mike McCandless)
4. LUCENE-959: Remove synchronization in Document (yonik)
5. LUCENE-963: Add setters to Field to allow for re-using a single
Field instance during indexing. This is a sizable performance
gain, especially for small documents. (Mike McCandless)
6. LUCENE-939: Check explicitly for boundary conditions in FieldInfos
and don't rely on exceptions. (Michael Busch)
7. LUCENE-966: Very substantial speedups (~6X faster) for
StandardTokenizer (StandardAnalyzer) by using JFlex instead of
JavaCC to generate the tokenizer.
(Stanislaw Osinski via Mike McCandless)
8. LUCENE-969: Changed core tokenizers & filters to re-use Token and
TokenStream instances when possible to improve tokenization
performance (~10-15%). (Mike McCandless)
9. LUCENE-871: Speedup ISOLatin1AccentFilter (Ian Boston via Mike
McCandless)
10. LUCENE-986: Refactored SegmentInfos from IndexReader into the new
subclass DirectoryIndexReader. SegmentReader and MultiSegmentReader
now extend DirectoryIndexReader and are the only IndexReader
implementations that use SegmentInfos to access an index and
acquire a write lock for index modifications. (Michael Busch)
11. LUCENE-1007: Allow flushing in IndexWriter to be triggered by
either RAM usage or document count or both (whichever comes
first), by adding symbolic constant DISABLE_AUTO_FLUSH to disable
one of the flush triggers. (Ning Li via Mike McCandless)
12. LUCENE-1043: Speed up merging of stored fields by bulk-copying the
raw bytes for each contiguous range of non-deleted documents.
(Robert Engels via Mike McCandless)
13. LUCENE-693: Speed up nested conjunctions (~2x) that match many
documents, and a slight performance increase for top level
conjunctions. (yonik)
14. LUCENE-1098: Make inner class StandardAnalyzer.SavedStreams static
and final. (Nathan Beyer via Michael Busch)
Documentation
1. LUCENE-1051: Generate separate javadocs for core, demo and contrib
classes, as well as an unified view. Also add an appropriate menu
structure to the website. (Michael Busch)
2. LUCENE-746: Fix error message in AnalyzingQueryParser.getPrefixQuery.
(Ronnie Kolehmainen via Michael Busch)
Build
1. LUCENE-908: Improvements and simplifications for how the MANIFEST
file and the META-INF dir are created. (Michael Busch)
2. LUCENE-935: Various improvements for the maven artifacts. Now the
artifacts also include the sources as .jar files. (Michael Busch)
3. Added apply-patch target to top-level build. Defaults to looking for
a patch in ${basedir}/../patches with name specified by -Dpatch.name.
Can also specify any location by -Dpatch.file property on the command
line. This should be helpful for easy application of patches, but it
is also a step towards integrating automatic patch application with
JIRA and Hudson, and is thus subject to change. (Grant Ingersoll)
4. LUCENE-935: Defined property "m2.repository.url" to allow setting
the url to a maven remote repository to deploy to. (Michael Busch)
5. LUCENE-1051: Include javadocs in the maven artifacts. (Michael Busch)
6. LUCENE-1055: Remove gdata-server from build files and its sources
from trunk. (Michael Busch)
7. LUCENE-935: Allow to deploy maven artifacts to a remote m2 repository
via scp and ssh authentication. (Michael Busch)
8. LUCENE-1123: Allow overriding the specification version for
MANIFEST.MF (Michael Busch)
Test Cases
1. LUCENE-766: Test adding two fields with the same name but different
term vector setting. (Nicolas Lalevée via Doron Cohen)
例子:
Select *
FROM (((Member INNER JOIN MemberSort ON Member.MemberSort=MemberSort.MemberSort) INNER JOIN MemberLevel ON Member.MemberLevel=MemberLevel.MemberLevel) INNER JOIN MemberIdentity ON Member.MemberIdentity=MemberIdentity.MemberIdentity) INNER JOIN Wedlock ON Member.Wedlock=Wedlock.Wedlock
orDER BY MemberDate DESC
内连接的功能是，把两个表相关联的记录列出来，必须是相关联的记录。
2) 左外连接，left outer join ... on
语句格式:
FROM [表名1] LEFT JOIN [表名2]
ON [表名1.字段A] 〈关系运算符〉[表名2.字段B]
其实LEFT JOIN 的功能就是将LEFT左边的表名1中的所有记录全部保留，而将右边的表名2中的字段B与表名1.字段A相对应的记录显示出来(当使用Select * 时)。而RIGHT JOIN 和LEFT JOIN 相反。
外连接的功能是，把LEFT左边的表中的所有记录保留，而右边表只保留相关联的记录,也就是先执行一次INNER JOIN,然后把LEFT左边的表中的与右边表没有任何关联的记录也保留，而右边表的字段为null.
3) 右外连接，right outer join ... on
与 left join左右相反。
4) 全连接，full join ... on(不常使用，只能用于outer)
功能结合了以上三种联军，先执行一次inner join,然后把两个表的多余字段都保留，但连接的对应字段为null.
如果想将几个表联接起来，在JOIN操作中我们可以进行嵌套操作，有三个表：表1、表2、表3，现在将三个表联接起来：
FROM （表1 INNER JOIN 表2 ON 表1.序号=表2.序号）
INNER JOIN 表3 ON 表1.序号=表3.序号
=====================
在一个正规化的数据库环境中, 我们常会碰到这款情形: 所需的资料并不是放在同一个资料表中, 在这个时候, 你就要用到 Join
当然 Join 如何将不同的数据库的资料结合, 还要看你如何使用它, 一共有四种不同的 Join 的方式, 在这篇文章中我们将为你介绍 Inner Join 及 Outer Join 以及其应用
Inner Join
Inner Join 应该是最常用的 Join 方式, 它只会传回符合 Join 规则的纪录, 还是先来看看语法
Select <要选择的字段> From <主要资料表>
<Join 方式> <次要资料表> [On <Join 规则>]
现在我们利用 MS SQL 内建的北风数据库来实际练习一下! 想多了解 MS SQL 的内建数据库, 你可以看看 SQL Server 的内建数据库 这篇文章
请打开 QA (Query Analyzer), 为了使用北风数据库, 请先执行 Use Northwind, 然后执行
Select ProductId, ProductName, SupplierId From Products
从 Products 产品资料表中取出三个字段, 分别是产品代码, 产品名称, 供货商代码, 但查询出来的结果保证让你的老板很不满意, 因为供货商代码对于人类实在是无虾米意义, 这个时候 Join 就可以帮上忙了, 藉由 Join Suppliers 这个资料表我们便可以查询到供货商名称
Select ProductId, ProductName, Suppliers.SupplierId
From Products
Inner Join Suppliers
Products.Suppliers = Suppliers.SupplierId
这款的查询结果是不是卡清楚呢! Inner Join 的主要精神就是 exclusive , 叫它做排他性吧! 就是讲 Join 规则不相符的资料就会被排除掉, 譬如讲在 Product 中有一项产品的供货商代码 (SupplierId), 没有出现在 Suppliers 资料表中, 那么这笔记录便会被排除掉
Outer Join
这款的 Join 方式是一般人比较少用到的, 甚至有些 SQL 的管理者也从未用过, 这真是一件悲哀的代志, 因为善用 Outer Join 是可以简化一些查询的工作的, 先来看看 Outer Join 的语法
Select <要查询的字段> From <Left 资料表>
<Left | Right> [Outer] Join <Right 资料表> On <Join 规则>
语法中的 Outer 是可以省略的, 例如你可以用 Left Join 或是 Right Join, 在本质上, Outer Join 是 inclusive, 叫它做包容性吧! 不同于 Inner Join 的排他性, 因此在 Left Outer Join 的查询结果会包含所有 Left 资料表的资料, 颠倒过来讲, Right Outer Join 的查询就会包含所有 Right 资料表的资料, 接下来我们还是来做些实际操作, 仍然是使用北风数据库, 但要先做一些小小的修改, 才能达到我们要的结果
首先要拿掉 Products 资料表的 Foreign Key, 否则没有法度在 Products 资料表新增一笔 SupplierId 没有对映到 Suppliers 资料表的纪录, 要知影一个资料表的 Constraint 你可以执行 SQL 内建的 sp_helpconstraint , 在 QA 执行
sp_helpconstraint Products
接下来删除 FK_Products_Suppliers 这个 Foreign Key
Alter Table Products
Drop Constraint FK_Products_Suppliers
再来新增一笔纪录于 Products 资料表, SupplierId 使用 50 是因为它并没有对映到 Suppliers 资料表中的记录
Insert Into Products (ProductName,SupplierId,CategoryId)
values ('Test Product','50','1')
现在我们再执行头前的查询, 只是将 Inner Join 改为 Left Outer Join
Select ProductId, ProductName, Suppliers.SupplierId
From Products
Left Outer Join Suppliers
Products.Suppliers = Suppliers.SupplierId
比较一下两种 Join 方式的查询结果, 你应该就会知影其中的差别!
再来看看 Right Outer Join, 请新增下底这笔记录
Insert Into Suppliers (CompanyName)
values ('LearnASP')
现在请使用 Right Out Join 来作查询, 比较看看查询的结果和 Inner Join 有什么不同!
寻找不相符纪录
这里我们来看看如何使用 Out Join 来找不相符纪录, 可能是有子纪录却没有父纪录或是颠倒过来
Select Suppliers.CompanyName From Products
Right Join Suppliers
On Products.SupplierId = Suppliers.SupplierId
Where Products.SupplierId is Null
执行结果你会找到一笔资料为 LearnASP, 该笔供货商资料存在, 但基本上已经没有产品是来自这个供货商, 想象一下如果不用 Outer Join 你要怎么以一个 SQL 指令完成同一查询结果! 知道 Outer Join 的好用了吧! 再执行
Select Products.ProductName
From Products
Left Join Suppliers
On Products.SupplierId = Suppliers.SupplierId
Where Suppliers.SupplierId is Null
这个查询结果你会发现 Test Product 这项产品竟然找不到供货商的资料!
输入出结果格式是这样的：
如：我输入“请在此处输入中文”
输出结果为：
qing-14357
zai-11046
ci-19253
chu-19290
shu-13596
ru-14101
zhong-10544
wen-12604
关面是拼音 ，后面是算出来的代号（为什么得到这样的数字，我也不知道），如果有时汉字不常用，没有加入，就只会显示出来代号，而不显示拼音，此时，你可以将其加入到里面就行了，格式如：ht.put("-10247","zz");
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