判断表是否存在方法1：
SELECT case WHEN a.cc =1 THEN 2 else 0 END FROM ( select count(*) as cc from pg_class where relname = 'wo' --wo is table name，pg_class是pg自带的关键字 ) as a
方法2：
用if判断，但有以下条件
The IF statement is part of the default procedural language PL/pgSQL. You need to create a function or execute an ad-hoc statement with the DO command.、
exist使用要求和if一样
DO $do$ BEGIN IF (select count(*) cc from pg_class where relname = 'wo') = 0 --一定要加括号 THEN INSERT INTO wo VALUES (2); ELSE INSERT INTO wo VALUES (1); END IF; END $do$
联合使用select 和insert的方法如下
create table language_ko(Key text,XML text); insert into Language_ko(key,xml) (select "Key " as key,'<'||"Key"||'>'||"Korean"||'</'||"Key"||'>' as xml from "centralClient1")
