学习SQL语句的很好的入门资料，包含各种语句详解，或是将以前学习的内容回顾一下,比较不错的电子书。
《最易入门SQL语句教程》目录：
SQL语句教程(01) SELECT.......................................2 
SQL语句教程(02) DISTINCT.....................................2 
SQL语句教程(03) WHERE........................................2 
SQL语句教程(04) AND OR ......................................3 
SQL语句教程(05) IN ..........................................3 
SQL语句教程(06) BETWEEN......................................4 
SQL语句教程(07) LIKE.........................................4 
SQL语句教程(08) ORDER BY.....................................5 
SQL语句教程(09)  函数........................................5 
SQL语句教程(10) COUNT .......................................6 
SQL语句教程(11) Group By ....................................6 
SQL语句教程(12) HAVING.......................................7 
SQL语句教程(13) ALIAS........................................7 
SQL语句教程(14)  连接........................................8 
SQL语句教程(15)  外部连接....................................9 
SQL语句教程(16) Subquery ....................................9 
SQL语句教程(17) UNION........................................10 
SQL语句教程(18) UNION ALL.................................. 11 
SQL语句教程(19) INTERSECT................................. 11 
SQL语句教程(20) MINUS........................................12 
SQL语句教程(21) Concatenate...................................12 
SQL语句教程(22) Substring ....................................13 
SQL语句教程(23) TRIM..........................................14 
SQL语句教程(24) Create Table .................................14 
SQL语句教程(25) Create View...................................15 
SQL语句教程(26) Create Index..................................16 
SQL语句教程(27) Alter Table...................................16 
SQL语句教程(28)  主键.........................................18 
SQL语句教程(29)  外来键.......................................18 
SQL语句教程(30) Drop Table....................................19 
SQL语句教程(31) Truncate Table ...............................20 
SQL语句教程(32) Insert Into...................................20 
SQL语句教程(33) Update .......................................20 
SQL语句教程(34) Delete .......................................21