Ulungelelwaniso lomanyano ngombuzo wesintaksi/usetyenziso lwengxelo kwisiseko sedatha seMySQL

MySQL databaseUlungelelwaniso lomanyano ngombuzo wesintaksi/usetyenziso lwengxelo

MySQL Umsebenzisi we-UNION

Le tutorial ikwazisa kwisintaksi kunye nemizekelo yomsebenzisi weMySQL UNION.

inkcazo

Umsebenzisi we-MySQL UNION usetyenziselwa ukudibanisa iziphumo zeengxelo ezimbini okanye ngaphezulu KHETHA kwiseti yesiphumo esisodwa.Iingxelo ezininzi KHETHA zisusa idatha ephindwe kabini.

Igrama

Ifomati yesivakalisi se-MySQL UNION yomsebenzisi:

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

IParamu

• intetho1, ibinzana2, ... intetho_n: Ikholamu eza kufunyanwa.
• iitafile: Itheyibhile yedatha enokufunyanwa.
• APHO iimeko: Ukhetho, iindlela zokukhangela.
• EZAHLUKENEYO: Ngokuzithandela, susa idatha ephindwe kabini kwiseti yeziphumo.Umsebenzisi we-UNION ukhuphe idatha ngokungagqibekanga, ngoko ke isilungisi se-DISTINCT asinasiphumo kwisiphumo.
• BONKE: Kukhethwa, ibuyisela zonke iziphumo, kuquka neziphindwayo.

idemo database

Kule tutorial, siza kusebenzisa i-database yesampula ye-chenweiliang.

Nantsi idatha evela kwitheyibhile "yeWebhusayithi":

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     |
+----+---------------+---------------------------+-------+---------+

Nantsi idatha ye-"apps" 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)

Umzekelo we-SQL UNION

Le nkcazo ilandelayo yeSQL ikhetha zonke kwi "Websites" kunye nee "apps" iitafileeyahlukileyoilizwe (kuphela amaxabiso ahlukeneyo):

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

SQL UNION WONKE umzekelo

Le ngxelo ilandelayo ye-SQL isebenzisa i-UNION BONKE ukukhetha kwi-"Websites" kunye neetafile ze-"apps".konkeilizwe (likwanexabiso eliphindiweyo):

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

SQL UNION ZONKE nge APHO

Le ngxelo ilandelayo ye-SQL isebenzisa i-UNION BONKE ukukhetha kwi-"Websites" kunye neetafile ze-"apps".konkeIdatha ye-China (CN) (kunye nexabiso eliphindwe kabini):

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