doc-exports/docs/dws/tool/dws_16_0152.html

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

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

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";

Parent topic: Table (Optional Parameters and Operations)