Aṣẹ ẹgbẹ nipasẹ ibeere sintasi/lilo alaye ni aaye data MySQL

Ibi ipamọ data MySQL UNION ORDER BY ìbéèrè syntax/gbólóhùn lílo

MySQL Oṣiṣẹ UNION

Ikẹkọ yii ṣafihan ọ si sintasi ati awọn apẹẹrẹ ti oniṣẹ MySQL UNION.

apejuwe

Oṣiṣẹ MySQL UNION ni a lo lati ṣajọpọ awọn abajade ti awọn alaye YAN meji tabi diẹ sii sinu eto abajade ẹyọkan.Awọn alaye YAN pupọ yọ awọn data ẹda-iwe kuro.

girama

MySQL UNION ọna kika sintasi oniṣẹ:

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

Apaadi

• ikosile1, ikosile2, ... ikosile_n: Ọwọn lati gba pada.
• awọn tabili: Tabili data lati gba pada.
• Nibo awọn ipo: Iyan, àwárí àwárí mu.
• YÀTỌ: Ni iyan, yọ data ẹda-iwe kuro ninu eto abajade.Oniṣẹ UNION ti yọkuro data nipasẹ aiyipada, nitorinaa iyipada DISTINCT ko ni ipa lori abajade.
• GBOGBO: Iyan, da gbogbo awọn eto abajade pada, pẹlu awọn ẹda-ẹda.

demo database

Ninu ikẹkọ yii, a yoo lo aaye data ayẹwo chenweiliang.

Eyi ni data lati tabili "Awọn aaye ayelujara":

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

Eyi ni data fun “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)

SQL UNION apẹẹrẹ

Gbólóhùn SQL tó tẹ̀lé yìí yan gbogbo àwọn orílẹ̀-èdè tó yàtọ̀ (àwọn iye tó yàtọ̀ nìkan) láti inú àwọn tábìlì "Wẹ́ẹ̀bùsáìtì" àti "àwọn ìṣàfilọ́lẹ̀" :

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

SQL UNION GBOGBO apẹẹrẹ

Gbólóhùn SQL tó tẹ̀lé yìí lo UNION ALL láti yan gbogbo orílẹ̀-èdè (pẹ̀lú àwọn iye méjì) láti inú àwọn tábìlì "Wẹ́ẹ̀bùsáìtì" àti "àwọn ìṣàfilọ́lẹ̀" :

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

SQL UNION GBOGBO pẹlu Nibo

Gbólóhùn SQL tó tẹ̀lé yìí lo UNION ALL láti yan gbogbo dátà fún China (CN) láti inú àwọn tábìlì "Wẹ́ẹ̀bùsáìtì" àti "àwọn ìṣàfilọ́lẹ̀" (pẹ̀lú àwọn iye onípele méjì):

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