准备：
sql语句为：
create table a1 (a int);
create table a2 (a int);
create table a3 (a int,b int);
create table a4 (a int,b int);
insert into a1 values (0),(1);//(被除数)(除数)
insert into a2 values (0),(0);//
(被除数)(除数)
insert into a3 values (0,0),(1,1);//
(被除数，测试数)(除数，测试数)
insert into a4 values (0,1),0);//
(被除数，测试数)(除数，测试数)
需要知道的：
select 4/0;
ERROR: division by zero
select * from a1 where (4 / a > 2) and (a > 0);//
(4 / a > 2) a有可能为0
返回1;
select * from a1 where (4 / a > 2) and (a > a-1);
ERROR: division by zero
select * from a2 where (4 / a > 2) and (a > 0);
无返回；
select * from a3 where (4 / a > 2) and (b > 0);
返回1;
select * from a4 where (4 / a > 2) and (b > 0);
ERROR: division by zero
当没有and时，执行计划会根据通过语法解析的节点复杂度进行重新排序，而有or的时候，就会按照手写的顺序。
原文链接：https://www.f2er.com/postgresql/196199.html