Help Center> Data Warehouse Service (DWS)> Tool Guide> DSC> SQL Syntax Migration Reference> MySQL Syntax Migrating> Schema Objects and Data Definition Language (DDL)> Table (Optional Parameters and Operations)> UNION
Updated on 2024-04-28 GMT+08:00
View PDF

UNION

UNION is a table creation parameter of the MERGE storage engine. Creating a table using this keyword is similar to creating a common view. The created table logically combines the data of multiple tables that are specified by UNION. DSC migrates this feature to the view creation statement in GaussDB.

Input

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
 
CREATE TABLE t1 (
    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    message CHAR(20)
) ENGINE=MyISAM;

CREATE TABLE t2 (
    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    message CHAR(20)
) ENGINE=MyISAM;

CREATE TABLE total (
    a INT NOT NULL AUTO_INCREMENT,
    message CHAR(20))
ENGINE=MyISAM UNION=(t1,t2) INSERT_METHOD=LAST;

Output

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
 
CREATE TABLE "public"."t1" (
    "a" SERIAL NOT NULL PRIMARY KEY,
    "message" CHAR(80)
)
WITH ( ORIENTATION = ROW, COMPRESSION = NO )
NOCOMPRESS
DISTRIBUTE BY HASH ("a");

CREATE TABLE "public"."t2" (
    a SERIAL NOT NULL PRIMARY KEY,
    message CHAR(80)
)
WITH ( ORIENTATION = ROW, COMPRESSION = NO )
NOCOMPRESS
DISTRIBUTE BY HASH ("a");

CREATE VIEW "public"."total"(a, message) AS
SELECT * FROM "public"."t1"
UNION ALL
SELECT * FROM "public"."t2";