Database

以下是摘自MySQL官方关于Select的语法，不过看上去有些复杂。
SELECT
    [ALL | DISTINCT | DISTINCTROW ]
      [HIGH_PRIORITY]
      [STRAIGHT_JOIN]
      [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
      [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
    select_expr [, select_expr ...]
    [FROM table_references
    [WHERE where_condition]
    [GROUP BY {col_name | expr | position}
      [ASC | DESC], ... [WITH ROLLUP]]
    [HAVING where_condition]
    [ORDER BY {col_name | expr | position}
      [ASC | DESC], ...]
    [LIMIT {[offset,] row_count | row_count OFFSET offset}]
    [PROCEDURE procedure_name(argument_list)]
    [INTO OUTFILE 'file_name' export_options
      | INTO DUMPFILE 'file_name'
      | INTO var_name [, var_name]]
    [FOR UPDATE | LOCK IN SHARE MODE]]

我做了些简化，如下
SELECT [DISTINCT] select_expr [, select_expr ...]
FROM table_references
WHERE where_condition
[GROUP BY {col_name | expr | position} [ASC | DESC]]
[HAVING where_condition]
[ORDER BY  {col_name | expr | position} [ASC | DESC]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

原文地址：http://dev.mysql.com/tech-resources/articles/mysql-set-datatype.html

最近经常被使用的一个MySQL数据类型不得不算SET数据类型了，SET数据类型是一个String类型，但是由于其涉及复杂的增加，所以常常作为一个组合类型被提及到。在创建表的时候，一个SET类型可以存储指定的字符串的预定义列表中的任何数量的字符串。从SET数据类型与ENUM数据类型的预定义字符集工作方式来说，他们是相似的，但是ENUM数据类型限制你的预定义字符串集合中的一个成员，SET数据类型容许你存储多个预定义字符串，没有任何一个字符串，或者所有的字符串，都可以。

在MySQL的表里面，SET数据类型是作为一个Integer值被存储的。根据可利用元素的数量，SET数据类型将占用了0到8个字节。

MySQL的SET数据类型的要求

The SET elements are stored in the MySQL table as a bitmap: each element is represented by a single bit. To demonstrate this, lets look at the following sample table, which will be the basis for the rest of this tutorial. (NOTE: In the examples that follow, there are never whitespaces between elements and their comma seperators. Also note that only during the definition of a set are the elements individually wrapped in single quotes, otherwise the set as a whole gets only one set of quotes. Please do likewise.)

在MySQL的表里面，SET元素当作一个bitmap来存储的：每个元素都通过一个单一比特来代表。为了说明这个，让我们来看看下面的表。