DQL:Data QueryLanguage 数据查询语言
select具体用法
SELECT select_list
[ INTO new_table ]
FROM table_source
[ WHERE search_condition ]
[ GROUP BY group_by_expression ]
[ HAVING search_condition ]
[ ORDER BY order_expression [ ASC | DESC ] ]
例子：找出emp表中员工号为007的员工的工资
SELECT t.sal
FROM emp t
WHERE t.ID =007
