SQL外链接操作学习备忘

Robert Su — Sun, 26 Jul 2009 08:12:00 GMT

SELECT b.id, b.name, a. COUNT
FROM (SELECT adminlevel, COUNT(*) AS [count]
        FROM hrdc.i_ins_info
        GROUP BY adminlevel) a, hrdc.b_adminlevel b
WHERE a.adminlevel =* b.id

或者写成

SELECT b.id, b.name, a. COUNT
FROM (SELECT gdfield, COUNT(*) AS [count]
        FROM hrdc.i_ins_info
        GROUP BY gdfield) a RIGHT JOIN
      hrdc.b_field b ON a.gdfield = b.id

这是右连接的一个例子

inner join(等值连接) 只返回两个表中联结字段相等的行
left join(左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录
right join(右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录
on 指定表间联结字段及其关系的等号 "=" 表达式, 返回 true 或 false. 当表达式返回 true 时, 则查询中包含该记录.

7.5.2

程序代码
Update (ctarticle AS a LEFT JOIN ctclass AS c ON a.classid = c.classid) LEFT JOIN cttag AS b ON a.articleid = b.articleid
SET tag=tag+' ', b.articleid=a.articleid, b.classid=a.classid, b.nclassid=a.nclassid
Where a.classid=23 AND a.nclassid=0 AND tagid is not null

7.5.1

程序代码
Update (ctarticle AS a LEFT JOIN (ctnclass AS c LEFT JOIN ctclass AS d ON c.classid = d.classid) ON a.nclassid = c.nclassid AND a.classid = c.classid) LEFT JOIN cttag AS b ON a.articleid = b.articleid SET tag=d.class+' '+c.nclass, b.articleid=a.articleid, b.classid=a.classid, b.nclassid=a.nclassid Where a.classid=23 AND a.nclassid=197;

7.5 更新操作

74.5 左连接中数据的筛选

程序代码
Insert INTO cttag(articleid,classid,nclassid) Select a.articleid,a.classid,a.nclassid from ctarticle a left join cttag b on a.articleid=b.articleid where b.articleid is null

//本语句功能为, 显示主表的全部内容, 插入数据到副表中没有的数据
//主要作用为: 让数据减少冗余

7.4.4.1 上例中的延续

程序代码
Select a.*, b.*, c.*, d.*
FROM cttag as d left join ((ctarticle AS a LEFT JOIN ctclass AS b ON a.classid=b.classid) LEFT JOIN ctnclass AS c ON a.nclassid=c.nclassid) on d.articleid=a.articleid;

7.4.4 显示文章表中的全部, 调用类别表中的栏目

程序代码
select a.*, b.*, c.* from (ctarticle a left join ctclass b on a.classid=b.classid) left join ctnclass c on a.nclassid=c.nclassid

//作用, 有时在文章表中包含了在个别类别表中没有的数据, 用这个语法可以读出文章表的全部数据
//a 为文章表, b 为主类别, c 为子类别

7.4.3 同上例, 选择追加数据时加上空格

程序代码
Insert INTO cttag(articleid,classid,nclassid,tag)
Select a.articleid,a.classid,a.nclassid,d.class+' '+c.nclass
FROM (ctarticle AS a left join (ctnclass c left join ctclass d on c.classid=d.classid) on a.classid=c.classid and a.nclassid=c.nclassid) LEFT JOIN cttag AS b ON a.articleid = b.articleid where a.classid=4 and a.nclassid=154;

7.4.2 连接N个表, 并追加数据到其中一个表, N=4

程序代码
Insert INTO cttag(articleid,classid,nclassid,tag)
Select a.articleid,a.classid,a.nclassid,d.class+c.nclass
FROM (ctarticle AS a left join (ctnclass c left join ctclass d on c.classid=d.classid) on a.classid=c.classid and a.nclassid=c.nclassid) LEFT JOIN cttag AS b ON a.articleid = b.articleid where a.classid=1 and a.nclassid=1;

//解读
插入到表2(栏1,栏2,栏3,栏4)
选择别名a.栏1, 别名a.栏2, 别名a.栏3, 别名d.栏4 加上别名c.栏5
从 (表1 别名a 左连接 (表3 别名c 左连接表4 别名d 在别名c.栏2 等于别名d.栏2) 在别名a.栏2 等于别名c.栏2 和别名a.栏3=别名c.栏3) 左连接表2 别名b 在别名a.栏1 等于别名b.栏1 在那里别名a.栏2=1 和别名a.栏3=1

7.4.1 连接两个表, 并追加数据到其中一个表

程序代码
Insert INTO cttag(articleid,classid,nclassid)
Select a.articleid,a.classid,a.nclassid
FROM ctarticle AS a LEFT JOIN cttag AS b ON a.articleid = b.articleid where a.classid=1 and a.nclassid=1;

//解读
插入到表2(栏1,栏2,栏3)
选择别名a.栏1, 别名a.栏2, 别名a.栏3
从表1 别名a 左连接表2 别名b 在别名a.栏1 等于别名b.栏1 在那里别名a.栏4=1 和别名a.栏5=1

7.4. 左连接

7.3.1 同步两表的数据

程序代码
Update ctarticle a INNER JOIN cttag b ON a.articleid = b.articleid SET b.classid=a.classid, b.nclassid=a.nclassid;

//解读
更新表1 别名a 联接表2 别名2 在别名a.栏1 等于别名b.栏1 设置别名b.栏2 更新为别名a.栏2, 别名b.栏3 更新为别名a.栏3

7.3 右外连接

程序代码
select a.*, b.* from bunclass a right join ctclass b on a.classid=b.classid where a.nclassid=20

查询别名 a,b 表, 只匹配 b 表中的内容.

7.2.3 添加数据到连接表之一

程序代码
Insert INTO cttag ( tag, articleid ) Select top 1 b.tag, a.articleid FROM ctarticle AS a left JOIN cttag AS b ON a.articleid = b.articleid Where a.articleid order by a.articleid desc;

7.2.2 变通中的用法二

程序代码
Insert INTO bureply
Select b.*, a.classid, a.nclassid
FROM article AS a INNER JOIN reply AS b ON a.articleid = b.articleid
Where classid=50;

7.2.1 实际应用中的变通

程序代码
Insert INTO butag ( tag, articleid, classid, nclassid)
Select b.tag, a.articleid, a.classid, a.nclassid
FROM article AS a INNER JOIN tag AS b ON a.articleid = b.articleid
Where classid=24;

7.2 添加数据到其他表

程序代码
Insert INTO butag ( tag, articleid )
Select b.tag, a.articleid
FROM article AS a INNER JOIN tag AS b ON a.articleid = b.articleid
Where a.articleid<>False;

//解读
添加到接收表(列1,列2)
选择别名b.列1, 别名a.列2
从表1 表名a 联接表2 表名b 在别名a.列c 等于别名b.列c
在哪里别名a.列c 不等于没有

7.1.1 实际应用中的变通

程序代码
Select b.tag, a.articleid, a.classid, a.nclassid
FROM article AS a INNER JOIN tag AS b ON a.articleid = b.articleid
Where a.classid=24;

7.1 查询

程序代码
Select b.tag, a.articleid
FROM article AS a INNER JOIN tag AS b ON a.articleid = b.articleid
Where a.articleid<>False;

//解读
选择别名b.列, 别名a.列
从表1 别名a 联接表2 别名b 在别名a.列c = 别名b.列c
在哪里别名a.列c 不等于没有
注: as 不是必要

7. 外连接——交叉查询

Robert Su 2009-07-26 16:12 发表评论

Oracle ：做数量统计的视图 & 更新的存储过程

Robert Su — Sat, 17 Jan 2009 02:56:00 GMT

create or replace view v_allinfo_stat_by_site as
select a.*,b.BLACK_COUNT,b.WHITE_COUNT,b.GRAY_COUNT,b.AUTHOR_COUNT,group_count,audit_count,vblog_org_count,valbum_count from v_video_stat_by_site a,
v_vblogger_stat_by_site b,
(select count(*) group_count,site_id from vblogger_group group by site_id) c ,
(select count(*) audit_count,site_id from audit_web_video group by site_id) d ,
(select count(*) vblog_org_count,site_id from vblogger_org group by site_id) e ,
(select count(*) valbum_count,site_id from valbum group by site_id) f
where a.site_id = b.site_id(+) and
a.site_id = c.site_id(+) and
a.site_id = d.site_id(+) and
a.site_id = e.site_id(+) and
a.site_id = f.site_id(+)
order by a.all_count desc;

c，d，e也是相当于视图
a、b本身就是视图

存储过程：
create or replace procedure UPDATE_VBLOGGER_MONTHLY_WEEKLY as
v_now_date NUMBER;
begin
--按月统计
   SELECT TO_NUMBER(TO_CHAR(sysdate,'YYYYMM'))INTO v_now_date FROM dual;
   update vblogger v set v.monthly_video_count=0;
   update vblogger v set v.weekly_video_count=0;
COMMIT;
   update vblogger v set v.monthly_video_count=(select count(*) from web_video w where GET_TIME_FORMAT(1,w.video_day)=v_now_date and v.site_id=w.site_id and v.name=w.video_author group by w.site_id,w.video_author) ;
--按周统计
     SELECT TO_NUMBER(TO_CHAR(sysdate,'YYYYFMWW'))INTO v_now_date FROM dual;
     update vblogger v set v.weekly_video_count=(select count(*) from web_video w where GET_TIME_FORMAT(3,w.video_day)=v_now_date and v.site_id=w.site_id and v.name=w.video_author group by w.site_id,w.video_author) ;
COMMIT;
end;

Robert Su 2009-01-17 10:56 发表评论

当日最热查询之SQL语句

Robert Su — Mon, 12 Jan 2009 13:55:00 GMT

之前做联合查询很慢也很麻烦；需要对web_video表跟webvideo _day视图做联合查询，但是速度奇慢
select a.* from web_video a webvideo b where a.id=b.id and a.site_id=?

换成这种方式之后就快多了
select a.* from web_video a where a.site_id=? and a.video_day=to_number(to_char(sysdate, 'yyyymmdd'));

video_day是一个物化视图 MATERIALIZED VIEW——可以大大提高数据库查询的速度。

Robert Su 2009-01-12 21:55 发表评论

BlogJava-workspace-随笔分类-数据库

SQL外链接操作学习备忘

Oracle ：做数量统计的视图 & 更新的存储过程

当日最热查询之SQL语句