select *(列名) from table_name(表名) where column_name operator
　　value
　　ex:(宿主)
　　select * from stock_information where stockid = str(nid)
　　stockname = 'str_name'
　　stockname like '% find this %'
　　stockname like '[a-zA-Z]%' --------- ([]指定值的范围)
　　stockname like '[^F-M]%' --------- (^排除指定范围)
　　--------- 只能在使用like关键字的where子句中使用通配符)
　　or stockpath = 'stock_path'
　　or stocknumber < 1000
　　and stockindex = 24
　　not stock*** = 'man'
　　stocknumber between 20 and 100
　　stocknumber in(10,20,30)
　　order by stockid desc(asc) --------- 排序，desc-降序，asc-升序
　　order by 1,2 --------- by列号
　　stockname = (select stockname from stock_information where
　　stockid = 4)
　　--------- 子查询
　　--------- 除非能确保内层select只返回一个行的值，
　　--------- 否则应在外层where子句中用一个in限定符
　　select distinct column_name form table_name ---------
　　distinct指定检索独有的列值，不重复
　　select stocknumber ,"stocknumber + 10" = stocknumber + 10 from
　　table_name
　　select stockname , "stocknumber" = count(*) from table_name
　　group by stockname
　　--------- group by 将表按行分组,指定列中有相同的值
　　having count(*) = 2 --------- having选定指定的组

　　select *
　　from table1, table2
　　where table1.id *= table2.id --------
　　左外部连接，table1中有的而table2中没有得以null表示
　　table1.id =* table2.id -------- 右外部连接

　　select stockname from table