Urutan Uni miturut sintaks pitakon / panggunaan statement ing database MySQL

database MySQLUrutan Uni miturut sintaksis pitakon / panggunaan pernyataan

MySQL operator UNION

Tutorial iki ngenalake sampeyan sintaks lan conto operator MySQL UNION.

Gambar

Operator MySQL UNION digunakake kanggo nggabungake asil saka loro utawa luwih statement SELECT dadi siji set asil.Multiple SELECT statements mbusak data duplikat.

toto wicoro

Format sintaks operator MySQL UNION:

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

Paramèter

• ekspresi1, ekspresi2, ... ekspresi_n: Kolom kanggo njupuk.
• tabel: Tabel data kanggo njupuk.
• Syarat WHERE: Opsional, kritéria telusuran.
• bedane: Opsional, mbusak data duplikat saka set asil.Operator UNION wis ngilangi data kanthi standar, mula modifikasi DISTINCT ora ana pengaruhe ing asil.
• KABEH: Opsional, ngasilake kabeh set asil, kalebu duplikat.

database demo

Ing tutorial iki, kita bakal nggunakake database sampel chenweiliang.

Punika data saka tabel "Situs web":

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

Punika data kanggo "aplikasi" 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 conto

Pernyataan SQL ing ngisor iki milih kabeh saka tabel "Situs web" lan "aplikasi".bedanegara (mung nilai sing beda):

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

SQL UNION ALL contone

Pernyataan SQL ing ngisor iki nggunakake UNION ALL kanggo milih saka tabel "Situs web" lan "aplikasi".kabehnegara (uga nduweni nilai duplikat):

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

SQL UNION ALL karo WHERE

Pernyataan SQL ing ngisor iki nggunakake UNION ALL kanggo milih saka tabel "Situs web" lan "aplikasi".kabehData kanggo China (CN) (uga kanthi nilai duplikat):

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