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更新时间：2024-06-29 GMT+08:00
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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

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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;

输出示例

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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";