]]>re: JUnit使用l验(1)(2)(3)http://www.aygfsteel.com/sybil/archive/2007/01/05/92031.html#92050SYBIL@BLOGJAVASYBIL@BLOGJAVAFri, 05 Jan 2007 09:45:00 GMThttp://www.aygfsteel.com/sybil/archive/2007/01/05/92031.html#92050MySQL支持下列用于SELECT语句的JOIN句法Q?
table_reference, table_reference
table_reference [CROSS] JOIN table_reference
table_reference INNER JOIN table_reference
table_reference STRAIGHT_JOIN table_reference
table_reference LEFT [OUTER] JOIN table_reference ON conditional_expr
table_reference LEFT [OUTER] JOIN table_reference USING (column_list)
table_reference NATURAL LEFT [OUTER] JOIN table_reference
{ oj table_reference LEFT OUTER JOIN table_reference ON conditional_expr }
上述最后的LEFT OUTER JOIN的句法只是ؓ了与ODBC兼容而存在的?
一个表可以是用aliasedtbl_name AS alias_name或tbl_name alias_name的v的别名?
mysql> select t1.name, t2.salary from employee AS t1, info AS t2
where t1.name = t2.name;
INNER JOIN?Q逗号)在语义上是等LQ都是进行一个在使用的表之间的全联结。通常Q你指定表应该如何用WHERE条g联结h?
ON条g是可以用在一个WHERE子句形式的Q何条件?
如果在一个LEFT JOIN中没有右表的匚w记录Q一个所有列讄为NULL的行被用于右表。你可以使用q个事实指出表中在另一个表中没有对应记录的记录Q?
mysql> select table1.* from table1
LEFT JOIN table2 ON table1.id=table2.id
where table2.id is NULL;
USING (column_list)子句命名一pd必须存在于两个表中的列?例如一个USING子句Q?
A LEFT JOIN B USING (C1,C2,C3,...)
被定义成在语义上{同一个这LON表达式:
A.C1=B.C1 AND A.C2=B.C2 AND A.C3=B.C3,...
2个表的NATURAL LEFT JOIN被定义ؓ在语义上{同于一个有USING子句命名在两表中存在的所有列的一个LEFT JOIN?
STRAIGHT_JOIN{同于JOINQ除了左表在双之前被读入,q能用于q些情况Q联l优化器表的顺序放错了?
一些例子:
mysql> select * from table1,table2 where table1.id=table2.id;
mysql> select * from table1 LEFT JOIN table2 ON table1.id=table2.id;
mysql> select * from table1 LEFT JOIN table2 USING (id);
mysql> select * from table1 LEFT JOIN table2 ON table1.id=table2.id
LEFT JOIN table3 ON table2.id=table3.id;
]]>re: 致老大和同志们书,zz from 老徐http://www.aygfsteel.com/sybil/archive/2006/12/13/86654.html#87551SYBIL@BLOGJAVASYBIL@BLOGJAVAWed, 13 Dec 2006 10:33:00 GMThttp://www.aygfsteel.com/sybil/archive/2006/12/13/86654.html#87551
]]>re: blog read of nov 18thhttp://www.aygfsteel.com/sybil/archive/2006/11/18/81975.html#81977SYBIL@BLOGJAVASYBIL@BLOGJAVASat, 18 Nov 2006 14:58:00 GMThttp://www.aygfsteel.com/sybil/archive/2006/11/18/81975.html#81977http://www.cnblogs.com/jackei/archive/2005/04/14/137461.html
]]>re: blog read of nov 18thhttp://www.aygfsteel.com/sybil/archive/2006/11/18/81975.html#81976SYBIL@BLOGJAVASYBIL@BLOGJAVASat, 18 Nov 2006 14:47:00 GMThttp://www.aygfsteel.com/sybil/archive/2006/11/18/81975.html#81976http://www.cnblogs.com/jackei/archive/2005/04/30/148281.html