我在Postgres 9.1中有一个简单的表格创建脚本.我需要它来创建表格
CREATE TABLE IF NOT EXISTS "mail_app_recipients"
(
"id_draft" Integer NOT NULL,
"id_person" Integer NOT NULL
) WITH (OIDS=FALSE); -- this is OK
ALTER TABLE "mail_app_recipients" ADD PRIMARY KEY IF NOT EXISTS ("id_draft","id_person");
-- this is problem since "IF NOT EXISTS" is not allowed.
如何解决这个问题?提前谢谢.