Dongosolo la mgwirizano pogwiritsa ntchito mawu amtundu / mawu mu database ya MySQL

MySQL databaseDongosolo la mgwirizano pogwiritsa ntchito mawu amtundu / mawu

MySQL Wothandizira UNION

Phunziroli likukudziwitsani za syntax ndi zitsanzo za opareshoni ya MySQL UNION.

kufotokoza

Wogwiritsa ntchito MySQL UNION amagwiritsidwa ntchito kuphatikiza zotsatira za mawu awiri kapena angapo SELECT kukhala chotsatira chimodzi.Zonena zingapo za SELECT zimachotsa zobwereza.

galamala

MySQL UNION mawonekedwe a syntax:

SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions]
UNION [ALL | DISTINCT]
SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions];

Parameti

• mawu1, mawu2, ... mawu_n: Mzere woti mutenge.
• matebulo: Dongosolo la data kuti mutenge.
• KUTI zikhalidwe: Zosankha, zofufuza.
• DISTINCT: Mwachidziwitso, chotsani deta yobwereza kuchokera pazotsatira.Wogwiritsa ntchito UNION adachotsa deta mwachisawawa, kotero chosinthira cha DISTINCT sichimakhudza zotsatira zake.
• ZONSE: Mwachidziwitso, imabweretsa zotsatira zonse, kuphatikizapo zobwereza.

demo database

Mu phunziro ili, tidzagwiritsa ntchito chitsanzo cha chenweiliang database.

Nayi zomwe zachokera patebulo la "Mawebusayiti":

mysql> SELECT * FROM Websites;
+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘宝          | https://www.taobao.com/   | 13    | CN      |
| 3  | 陈沩亮博客      | http://www.chenweiliang.com/    | 4689  | CN      |
| 4  | 微博          | http://weibo.com/         | 20    | CN      |
| 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |
| 7  | stackoverflow | http://stackoverflow.com/ |   0 | IND     |
+----+---------------+---------------------------+-------+---------+

Nayi data ya "mapulogalamu" APP:

mysql> SELECT * FROM apps;
+----+------------+-------------------------+---------+
| id | app_name   | url                     | country |
+----+------------+-------------------------+---------+
|  1 | QQ APP     | http://im.qq.com/       | CN      |
|  2 | 微博 APP | http://weibo.com/       | CN      |
|  3 | 淘宝 APP | https://www.taobao.com/ | CN      |
+----+------------+-------------------------+---------+
3 rows in set (0.00 sec)

Chitsanzo cha SQL UNION

Mawu otsatirawa a SQL amasankha zonse kuchokera pa "Websites" ndi "mapulogalamu" matebulozosiyanadziko (zosiyana zokhazokha):

SELECT country FROM Websites
UNION
SELECT country FROM apps
ORDER BY country;

SQL UNION zitsanzo ZONSE

Mawu otsatirawa a SQL amagwiritsa ntchito UNION ONSE kusankha pa "Mawebusayiti" ndi "mapulogalamu" matebulozonsedziko (lilinso ndi zobwerezabwereza):

SELECT country FROM Websites
UNION ALL
SELECT country FROM apps
ORDER BY country;

SQL UNION ONSE ndi KUTI

Mawu otsatirawa a SQL amagwiritsa ntchito UNION ONSE kusankha pa "Mawebusayiti" ndi "mapulogalamu" matebulozonseZambiri zaku China (CN) (komanso zobwerezedwanso):

SELECT country, name FROM Websites
WHERE country='CN'
UNION ALL
SELECT country, app_name FROM apps
WHERE country='CN'
ORDER BY country;