数据仓库服务 GaussDB(DWS)-UNION

时间：2025-02-12 15:05:07

UNION

UNION 是 MERGE 引擎的建表参数。通过该关键字建表类似于创建普通视图。新创建的表将在逻辑上合并UNION关键字限定的多个表的数据。DSC迁移时会将该特性转为 GaussDB 视图创建语句。

输入示例

     
          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;

输出示例

     
          CREATE TABLE "public"."t1" (    "a" SERIAL NOT NULL PRIMARY KEY,    "message" CHAR(80))WITH ( ORIENTATION = ROW, COMPRESSION = NO )NOCOMPRESSDISTRIBUTE BY HASH ("a");CREATE TABLE "public"."t2" (    a SERIAL NOT NULL PRIMARY KEY,    message CHAR(80))WITH ( ORIENTATION = ROW, COMPRESSION = NO )NOCOMPRESSDISTRIBUTE BY HASH ("a");CREATE VIEW "public"."total"(a, message) ASSELECT * FROM "public"."t1"UNION ALLSELECT * FROM "public"."t2";