Usoro otu site na iji syntax/nkwupụta ajụjụ na nchekwa data MySQL

MySQL nchekwa dataUsoro otu site na ajụjụ syntax/nkwupụta ojiji

MySQL Onye ọrụ UNION

Nkuzi a na-ewebata gị na syntax na atụ nke onye ọrụ MySQL UNION.

nkọwa

A na-eji onye ọrụ MySQL UNION jikọta rịzọlt nke abụọ ma ọ bụ karịa nkwupụta SELECT n'ime otu arụpụtaghị ihe.Ọtụtụ nkwupụta SELECT na-ewepụ data oyiri.

ụtọ asụsụ

Ọkpụkpọ syntax onye ọrụ MySQL UNION:

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

Paramita

• okwu1, okwu2, ... okwu_n: Ogidi iji weghachite.
• tebụl: Tebụl data iji weghachite.
• Ebe ọnọdụ: Nhọrọ, njirisi ọchụchọ.
• Ọpụrụiche: Nhọrọ, wepụ data oyiri na nsonaazụ nsonaazụ.Onye na-ahụ maka UNION ewepụtala data na ndabara, yabụ ihe mgbanwe DISTINCT enweghị mmetụta na nsonaazụ ya.
• Nile: Nhọrọ, na-eweghachite nsonaazụ nsonaazụ niile, gụnyere oyiri.

nchekwa data ngosi

N'ime nkuzi a, anyị ga-eji nchekwa data chenweiliang sample.

Nke a bụ data sitere na tebụl "Website":

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

Nke a bụ data maka "ngwa" 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 ihe atụ

Nkwupụta SQL na-esote na-ahọrọ ihe niile na tebụl "Website" na "ngwa".dị icheobodo (naanị ụkpụrụ dị iche):

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

SQL UNION ihe atụ niile

Nkwupụta SQL na-esonụ na-eji UNION ALL ịhọrọ site na "Website" na "ngwa" tebụlha niileobodo (nwerekwa ụkpụrụ oyiri):

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

SQL UNION niile nwere ebe

Nkwupụta SQL na-esonụ na-eji UNION ALL ịhọrọ site na "Website" na "ngwa" tebụlha niileData maka China (CN) (nwerekwa ụkpụrụ oyiri):

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