我就废话不多说了，大家还是直接看代码吧~
SELECT sum(aa) as "recordNumber" FROM table
SELECT sum(aa) as recordNumber FROM table
postgis查询字段是将字段字段转为小写，如果需要大写的字符，需要加双引号
补充：Postgresql中表名、列名、用户名大小写问题
注意：是双引号，单引号可能会被解析成普通字符，因而是不识别的字段
highgo=# create table "ExChange" (id int);
CREATE TABLE
highgo=# create table ExChange (id int);
CREATE TABLE
highgo=# \d
List of relations
Schema | Name | Type | Owner
----------------+----------+-------+--------
oracle_catalog | dual | view | highgo
public | ExChange | table | highgo
public | exchange | table | highgo
public | myt | table | highgo
public | t1 | table | highgo
public | tran | table | highgo
(6 rows)
highgo=# insert into exchange values (1);
INSERT 0 1
highgo=# insert into "ExChange" values (2);
INSERT 0 1
highgo=# select * FROM exchange ;
id
----
1
(1 row)
highgo=# select * FROM ExChange ;
id
----
1
(1 row)
highgo=# select * FROM "ExChange" ;
id
----
2
(1 row)
highgo=# insert into ExChange values (2);
INSERT 0 1
highgo=# select * FROM "ExChange" ;
id
----
2
(1 row)
highgo=# select * FROM exchange ;
id
----
1
2
(2 rows)
> 从上面可以看出，如果不加双引号，那么表名都会被转化为小写。如果想要大小写混用，需要添加双引号。
highgo=# create table exchange (ID int,id int);
ERROR: 42701: column "id" specified more than once
highgo=# create table exchange (ID int,name text);
CREATE TABLE
highgo=# select id from exchange ;
id
----
(0 rows)
highgo=# select ID from exchange ;
id
----
(0 rows)
highgo=# select "ID" from exchange ;
ERROR: 42703: column "ID" does not exist
LINE 1: select "ID" from exchange ;
highgo=# \d exchange
Table "public.exchange"
Column | Type | Modifiers
--------+---------+-----------
id | integer |
name | text |
highgo=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
aaa | | {}
gpadmin | Superuser, Create role, Create DB | {}
highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
replica | Replication | {}
highgo=# create table AAA;
ERROR: 42601: syntax error at or near ";"
LINE 1: create table AAA;
^
highgo=# create user AAA;
ERROR: 42710: role "aaa" already exists
highgo=# create user "AAA";
CREATE ROLE
highgo=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
AAA | | {}
aaa | | {}
gpadmin | Superuser, Create role, Create DB | {}
highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
replica | Replication | {}
实验证明，字段与用户同样会被自动转化为小写，除非添加双引号。 其实最好的办法就是全部用小写，这样才能尽量减少问题的出现。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。如有错误或未考虑完全的地方，望不吝赐教。
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