Help Center/ Data Warehouse Service / Tool Guide/ DSC/ MySQL Syntax Migrating/ Table (Optional Parameters and Operations)/ UNION
Updated on 2025-04-10 GMT+08:00
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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

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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

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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";