执行到以接受空值

execute format('select 1 where false') into t 不会把什么放在t上,所以以后 execute t

错误:EXECUTE的查询字符串参数为null

因此,简单的合并将有助于:

t=# do $$
declare t text;
begin
execute format('select 1 where %L',false) into t;
execute coalesce(t,'select now()') into t;
raise '%',t;
end;
$$
;
ERROR:  2017-07-11 16:11:03.149521+00
Time: 0.349 ms