Fa'atonuga fa'atasi e ala ile fa'aogaina ole syntax/fa'amatalaga ile MySQL database

MySQL databaseFa'atonuga fa'atasi e ala ile fa'aogaina ole fa'aoga/fa'amatalaga

MySQL fa'alapotopotoga a le UNION

O lenei aʻoaʻoga faʻafeiloaʻi oe i le syntax ma faʻataʻitaʻiga a le MySQL UNION operator.

faamatalaga

O le MySQL UNION operator e faʻaaogaina e tuʻufaʻatasia ai taunuʻuga o faʻamatalaga e lua pe sili atu SELECT i se seti se tasi.O fa'amatalaga SELECT e tele e aveese fa'amatalaga fa'alua.

kalama

MySQL UNION operator syntax faatulagaga:

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

Parakalafa

• fa'aaliga1, fa'aaliga2, ... fa'aaliga_n: Koluma e toe aumai.
• laulau: Le laulau fa'amaumauga e toe aumai.
• WHERE tulaga: Filifili, fa'avae su'esu'e.
• FA'AVAE: I le faitalia, aveese fa'amatalaga fa'alua mai le seti o fa'ai'uga.Ua to'esea e le fa'alapotopotoga a le UNION fa'amaumauga ona o le fa'aletonu, o lea e leai se a'afiaga o le fa'aliliuga DISTINCT i le fa'ai'uga.
• UMA: Filifili, toe fa'afo'i uma seti fa'ai'uga, e aofia ai fa'alua.

fa'amatalaga fa'amatalaga

I lenei aʻoaʻoga, o le a matou faʻaogaina le chenweiliang sample database.

O fa'amaumauga nei mai le laulau "Upega Tafa'ilagi":

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

O fa'amaumauga nei mo le "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 fa'ata'ita'iga

Ole fa'amatalaga SQL o lo'o mulimuli mai e filifilia uma mai le "Websites" ma "apps" laulaueseatunuu (na'o tulaga taualoa):

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

SQL UNION ALL fa'ata'ita'iga

O le fa'amatalaga SQL o lo'o fa'aaoga e UNION ALL e filifili ai mai le "Websites" ma le "apps" tablesumaatunu'u (e iai fo'i tulaga fa'atusa):

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

SQL UNION UMA ma WHERE

O le fa'amatalaga SQL o lo'o fa'aaoga e UNION ALL e filifili ai mai le "Websites" ma le "apps" tablesumaFa'amatalaga mo Saina (CN) (fa'atasi ai ma tau fa'alua):

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