维基百科重定向到一个关于“多层架构”的页面,上面写着:
In software engineering, multi-tier architecture (often referred to as n-tier
architecture) is a client–server architecture in which presentation, application
processing, and data management functions are logically separated.
这是不是就像使用mySQL创建和查询数据库,使用php进行交互,使用HTML进行表示一
嗨,我正在运行下面的代码。第一个查询返回了我需要的内容...我只想添加一个列来了解对象的环境。第二个查询不起作用,因为它查看'P‘和'T’列并比较
1)
proc sql;
create table ALL_compare_PROD_TEST as
(select * from PROD Except select * from TEST)
UNION ALL
(select * from TEST Except select * from PROD)
ORDER BY code ASC
;QUIT;
2)
proc sql;
create table ALL_com
我想写一个查询,在MySQL中打印从1到100的数字,但我似乎找不到任何解决方案。我试了几样东西
with CTE as
(
select 1 Number
union all
select Number +1 from CTE where Number<100
)
select *from CTE
但我不认为它在MySQL中有效
我有下面的递归函数,它可以工作...直到某一时刻。然后,一旦查询超过大约100次,脚本就会要求更多内存,当我添加更多内存时,脚本通常就会死掉(我最终在浏览器上看到一个白屏)。
public function returnPArray($parent=0,$depth=0,$orderBy = 'showOrder ASC'){
$query = mysql_query("SELECT *, UNIX_TIMESTAMP(lastDate) AS whenTime
FROM these_pages
WHERE parent
我想将一个有效的MySQL查询转换为PostgreSQL。我是PostgreSQL的纽比
工作MySQL查询:
select id,
user_name,
reported_to
from (select * from user_master
order by reported_to) orrdered,
(select @pv := 'prathap Achuthan') initialisation
where find_in_set(reported_to, @pv)
and leng
首先,我有一个问题,通过条件进行连接(在Oracle 12c中):
这是我的Oracle SQL:
SELECT
employee_id,
lpad(' ', level*2-1,' ') || last_name,
manager_id,
level,
SYS_CONNECT_BY_PATH(last_name, '/') "Path" --returns the full path of the child
FROM
hr.employees
start with em
在我的MySQL模式中,我有一个category(id, parentid, name)表
在MSSQL中,我使用了CTE查询(从下到上为提供的类别ID构建一个类别树:
with CTE (id, pid, name)
as
(
select id, parentid as pid,name
from category
where id = 197
union all
select CTE.pid as id , category.parentid as pid, category.name
from CTE
下面的查询运行得很好。我使用外部select中的值来过滤内部select中的值。
SELECT
bk.ID,
(SELECT COUNT(*) FROM guests WHERE BookingID = bk.ID) as count
FROM
bookings bk;
但是,以下select将不起作用:
SELECT
bk.ID,
(SELECT SUM(count) FROM (SELECT COUNT(*) AS count FROM guests WHERE BookingID = bk.ID GROUP BY RoomID) sub) as s
我试图了解MySQL递归查询是如何工作的,并以我想要的方式获取数据。
现在,我有以下SQL
SELECT `Library`.*, l2.*, l3.*
FROM `Library`
LEFT JOIN `Library` as `l2` on `l2`.`subsectionOf`=`Library`.`iD`
LEFT JOIN `Library` as `l3` on `l3`.`subsectionOf`=`l2`.`iD`
WHERE `Library`.`iD` = 0x02
ORDER BY `Library`.`subsectionOrder`, `l2`.`subsectio