mysql 手册这些该怎么理解？

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'
        [CHARACTER SET charset_name]
        export_options
      | INTO DUMPFILE 'file_name'
      | INTO var_name [, var_name]]
    [FOR UPDATE | LOCK IN SHARE MODE]]

from 一般查询都会用的，官网一些示例from是可以省略的，看这语法似乎也是可以省略的，那我如果完全是没接触的语句，就没法根据这个手册写出正确的语句了，我应该去哪里查阅帮住我正确使用这个手册

[]是可以忽略的，{}中的是任选其一，｜是选项的分隔符